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HIBRARY OF CONGRESS.; 

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f [SMITHSONIAN DEPOSIT.] t 

^UNITED STATES OF AMERICA. | 



PHYSICAL GEOGRAPHY, 



FOR 



FAMILIES AND SCHOOLS 



PHYSICAL GEOGRAPHY 



FOR 



FAMILIES AND SCHOOLS 



] 



Rp'M. ZORNLIN, 



AUTHOR OF "RECREATIONS IN PHYSICAL GEOGRAPHY," ETC. ETC. 



KEVISED, WITH A D D I T I IT S 



By WILLIAM L. GAGE 



LATE MASTER OF THE TAUSTOX HIGH SCHOOL. 



^-i^^-* 



BOSTON AND CAMBRIDGE : 
JAMES MUNROE AND COMPANY 

, M DCCC LV. 



I 



Entered according to Act of Congress, in the year 1855, by 

James Mttneoe and Company, 

In the Clerk's Office of the District Court of the District of Massachusetts. 



CAltfiRlBGE! 
THDRSTON AND TOKRT, PlilXTERS. 



CONTENTS 



PAGE 

Preface to the English Edition .... ix 

" " American *' xiii 

Note to the Teacher xv 

The Objects of Physical Geography .... 1 

The Earth 2 

Form of the Earth 2 

The Equator 4 

Diurnal and Annual Motions of the Earth . . 6 

Latitude and Longitude 9 

Latitude 9 

Circles . 10 

Zones 10 

Longitude ... .... 11 

Distribution of Land and "Water 14 

Continents 15 

Islands . . . 15 

Variations of the Surface . • . . . 17 

Mountains 17 

Table of Heights of Mountains .... 25 

Plateaus or Table Lands 27 



VI CONTENTS. 

PAGE 

Rain, Snow, and Hail ...... 88 

Plains or Lowlands 28 

Valleys 30 

The Sea-Level ....... 32 

GEOLoaY 33 

Rocks 33 

Earthy Formations, &c 34 

Earths 35 

Stratified Rocks , ,36 

Unstratified Rocks 38 

Volcanic Regions 39 

Earthquakes 41 

Metallic Veins 43 

The Wateks of the Globe ...... 45 

Springs 45 

Rivers . . ... . . . 50 

Table of Lengths of Rivers ^6 * 

Lakes 57 

The Ocean . . 60 

Tides, Waves, and Currents 68 

Tidal Wave 68 

Wind Waves . 70 

Currents of the Ocean 71 

The Atmosphere . . , . . . . 75 

Atmospheric Air . . ■ . . . . .75 

Weight of an Atmosphere 77 

The Barometer 77 

Winds 79 

Hurricanes . . 84 

Atmospheric Moisture 85 

Dew . . .86 

Mists and Fogs 87 

Clouds 88 



CONTENTS. 



vu 



Climate 

Diversity of Climate 

Height of Snow Line 

Isothermal Lines .... 

Isochimenal and Isotheral Lines 
Electricity and Magnetism 

Electricity ..... 

Terrestrial Magnetism 
Geographical Distribution of Plants , 

Classes of Plants .... 

Nourishment of Plants 

Botanical Regions .... 

Cultivation of the Cerealia 
Geographical Distribution of Animals 

Departments of the Animal Kingdom 

Animals of the Old and of the New World 

Range of Birds .... 

Gkographical Distribution of Man. . 

Languages of the World ... 

Varieties of the Human Race 

Conclusion 



Exercises for the Examination of Pupils 
Questions for Investigation 



Page 
95 
95 
99 
108 
108 
109 
109 
111 
114 
115 
118 
120 
125 
126 
126 
129 
130 

134 
134 
136 
139 
141 
153 



ILLUSTRATIONS. 

Page 

1. Diagram illustrative of the Rotundity of the Earth . 4 

2. Diagram illustrative of the Earth's Orbit . . .8 

3. Map showing the Principal Mountain Ranges of the 

Globe and the Currents of the Ocean ... 18 

4. Map of the Rainy and Rainless Districts of the Earth 92 

5. Height of Snow-Line in Different Latitudes . . .101 

6. Map of the Geographical Distribution of Man . . 134 



PKEPACE 

TO THE ENGLISH EDITION, 



Physical Geography has of late years become a 
subject of such general interest, and now takes so 
prominent a place among popular sciences, that some 
acquaintance with its aim and the views it unfolds 
may be considered as one of the requirements of edu- 
cation. To facilitate the attainment of this knowledge 
is the design of the present little work, in which the 
subject is placed before the reader in familiar lan- 
guage and in a concise form, thus adapting it not only 
for the scholar, but also for the parent and teacher, 
and for all who, from previous inattention to this 
branch of knowledge, may be desirous of forming a 
ready acquaintance with the leading principles of tlje 
science. 



X PREFACE. 

Physical Geography owes its present state of for- 
wardness to the combined observations of numerous 
individuals ; and perhaps may be considered as dating 
its great advance from the era of the general peace of 
1815 ; for it has only been subsequent to the cessation 
of war, that scientific men of various nations have ob- 
tained free access to different stations on the earth's 
surface, where observations have been successfully 
carried on ; and it is by the mutual interchange of 
information thus gathered, that a large portion of 
our knowledge of Physical Geography has been ac- 
quired. 

We have said that this science owes its great prog- 
ress to the combined observations of numerous indi- 
viduals ; — we may also add, that it invites its student 
to observe, to give his attention to all that its passing 
around him in the natural world, and to verify for 
himself, as far as circumstances will admit, the truth 
of the data thus presented to his view. He may even 
lend his aid to the furtherance of this science. In- 
stances are not wanting, both in our own day and in 
former times, of individuals from every class of society 
raising themselves to eminence by the pursuit of 
science ; and the path is open to all. The inhabitant 
of the country may, doubtless, in this respect possess 



PREFACE. XI 

greater advantages than the dweller in crowded cities ; 
he may take note of the minerals and plants in his own 
immediate neighborhood, or may devote his attention 
to the habits of birds and insects, and by recording his 
observations may contribute his quota to the general 
mass of knowledge. But the dweller in towns may 
also perform his part : he may observe the ever-vary- 
ing clouds, the temperature, the climate of the place 
of his abode. He, too, may enjoy opportunities denied 
to the other, of ready access to works of travels, and 
thus be enabled to trace the application of the knowl- 
edge he has acquired to all parts of the globe. Had 
our limits permitted, we would gladly have attempted 
this application in the present little treatise ; but having 
already in a former work,* with this especial object in 
view, carried our friends over the various regions of 
the earth, we must now content ourselves with tracing 
the Outlines of Physical Geography, trusting that 
these will be found of sufficient interest to induce our 
readers to pursue the subject into its more minute 

details. 

R. M. Z. 

* K^creations in Physical Geography. 



PREFACE 



TO THE AMERICAN EDITION. 



In the preparing of small school books, the English 
have an unquestionable superiority over us. Such 
treatises with them have the great merit of comprehen- 
siveness, and avoid both childish diffuseness and 
merely superficial views. This little work, which we 
take pleasure in introducing to American teachers, will 
suitably illustrate this. While its range is very broad ; 
while we are now lifted to the clouds, and anon carried 
fai' into the depths beneath our feet ; transported in a 
moment from ocean to ocean and from shore to shore, 
initiated into the manifold secrets of nature, and taught 
on every side the greatness and the wisdom and the 
love of the Creator and Father of us all, we see the 
chain which binds together all the sciences and makes 
them one. 



XIV PREFACE. 

And in the study of this comprehensive science of 
sciences, which is termed in one word Physics, we on 
this side of the Atlantic have made but little advance- 
ment. Still, the impulse which Maury and Guyot, 
Fremont and Agassiz and Bache have given to this 
department of human knowledge, will not lose its force 
till it is felt in our schools. The day is not distant 
when the study of Physical Geography will not only 
escape neglect, but will take the same rank in Ameri- 
can that it does in English schools. We hope that this 
little treatise will be the means in part of accomplish- 
ing this great end, and that in opening to the«young 
the riches of this science, it may tempt to a deeper 
search than this work can afford. Those who may 
have acquired some interest in the fascinating study of 
Physics, can gratify their curiosity by consulting the 
pages of Mrs. Somerville, Guyot, Wittich, Murray, and 
the larger work by the author of this treatise, while the 
most mature mind may reserve its strength for the 
broad generalizations of Humboldt's Kosmos. 

W. L. G. 

Boston, October, 1855. 



NOTE 

TO THE TEACHER, 



This work can be used by scholars of ordinary 
abilities from twelve to eighteen years of age. 
With the youngest class who may have it, let 
the teacher invent very numerous questions; to 
scholars of an older age, those at the close of 
the volume will suggest the contents of sen- 
tences, and in some cases of paragraphs ; the 
pupils of the first class will need no questions, 
but should give a summary of the contents of 
the lesson, omitting no fact, however unimpor- 
tant, yet not committing the words of the book 
to memory more than need be. 

Have the locality of every place mentioned in 
the book known and recited. 



XVI NOTE TO THE TEACHER. 

Have the meaning of all important words 
given, and accustom the scholars to give full 
explanations of phenomena like the currents, 
winds, &c. Accustom the pupils to a habit of 
getting collateral information from all som'ces, 
and expressing it freely in the class-room. 

Have the work known with perfect accuracy 
before it is laid aside, that the facts contained in 
it may be remembered through life. 



PHYSICAL GEOGRAPHY. 



I. THE OBJECTS OF PHYSICAL GEOGRAPHY. 

Physical Geography, or in other terms, Na- 
tural Geography, consists of a description of 
the Earth we inhabit, and directs our attention 
to its structure, to the waters on its surface, to its 
atmosphere, to its various animal, vegetable and 
mineral productions, and to the laws by which 
these are governed. 

It is called Physical or Natural Geography^ 
because it considers the Earth under its natural 
features, that is, according to the nature imparted 
to it by its Almighty Maker, and not in reference 
to any artificial divisions made by man into 
kingdoms and states. We are thus led to regard 
the Earth as one great whole ; and regions are 
determined by natural conditions, such as the 
climate or temperature of any portion of the 
Earth's surface, the prevalence or absence of 
particular species of plants, &c. 
1 



& , PHYSICAL GEOGRAPHY. 

Physical Geography is a science of great 
utility, because it makes us acquainted with 
much that tends to man's benefit and prosperity. 
It also forms a very gratifying pursuit, for it 
presents us with, numberless highly interesting 
facts in the natural world, which might other- 
wise pass unheeded, and it displays to our view 
the wisdom and goodness of the great Creator 
of the Universe. 



II. THE EARTH. 



The Earth belongs to a group or system of 
bodies termed planets, which revolve round the 
Sun, from which they derive both light and heat. 

The Earth is of a spherical or globular form. 
A sphere is a perfectly round body : this the 
Earth is not, being somewhat flattened (not un- 
like the usual shape of an orange) at the ex- 
tremities of its axis, which are called the north 
and south poles. The earth is accordingly not a 
perfect sphere, and is termed a spheroid. 

This spheroid is called oblate,, because it re- 
volves about its shortest diameter. The peculiar 
shape of the Earth is that which a soft globe 



THE EARTH. d 

assumes when put into rapid motion ; and the 
Earth is supposed to have been once in a soft 
state. 

The spherical form or rotundity of the Earth 
is proved by ships sailing round the globe. It is 
well known that Captain Cook and a host of 
other navigators have, by steering in either an 
eastward or westward direction (as nearly as the 
general arrangement of land and water will per- 
mit), ultimately returned to the same point from 
which they started. 

The globular form of the Earth is also proved 
by the appearance presented on the surface of 
the ocean. If the Earth were a flat plain, the 
distances would seem misty and ill-defined, in- 
stead of "which a sharp, clear, well-marked Une, 
called the horizon^ extends all round a vessel in 
the broad open sea, in the form of a circle, of 
which the vessel forms the centre. The undula- 
tions of the dry land, and the various objects on 
its surface, prevent us from observing this with 
any degree of certainty in the interior of a coun- 
try ; but if we stand on the sea shore, we may 
notice that the surface of the ocean is terminated 
by a clear distinctly-marked line, which consti- 
tutes the visible horizon. 

If while we are on the borders of the ocean, a 
vessel should put out to sea, a most excellent 



THE EARTH. 



opportunity will be afforded us of observing the 
globular form of the Earth, by watching this ves- 
sel as it recedes from the shore. The visible 
horizon may be considered as extending to the 
distance of about 30 miles from a person stand- 
ing on the beach. As the vessel recedes from 
the shore, it will diminish in size, but the whole 
will be visible until it reaches this water line. 
When it has passed this line, though the masts 
and sails will still remain in view, the huU of the 
ship will be below the horizon, the portion of the 
ocean on which it is sailing being concealed from 
the spectator by the globular form of the Earth, 
and at length the whole will be lost to his view. 




Thus, if the spectator were to stand on the 
sea shore sh, the visible horizon would extend on 
a level with the line h z n, and when the vessel 
had passed the portion of the sea to which that 
line extends at n, it would be descending what 
to the spectator at s forms the other side of the 
globular-shaped earth and the waters on its sur- 
face. 

The Earth, or globe, is divided into two equal 
parts by an imaginary line called the equator^ or 



THE EARTH. O 

equinoctial line, the upper portion (or half-sphere) 
of the ^ globe being distinguished as the northern 
hemisphere, and the lower portion as the southern 
hemisphere. 

Maps of the world are frequently divided into 
two circular portions, called the eastern and west- 
ern hemispheres. These have no marked division 
like that of the equator, which extends from east 
to west across these hemispheres, but they are 
useful as a mode of representing the form of a 
globular body like the Earth on a flat surface, 
and also as conveying an idea of the two great 
divisions of land on the face of the Earth. 

The circumference of the Earth, that is, its 
girth at the equator, where it is of greatest size, 
is nearly 25,000 miles. Its diameter, or the meas- 
ure of its ividth through the centre at that line, is 
rather less than one-third of its circumference, or 
about 7926 miles. In consequence of its being 
in some degree flattened at the poles, its diameter 
from north to south is about 26 miles less, or 
7900 miles. The diameter may be stated, in 
round numbers, at 8000 miles ; and the radius, 
or distance from the centre to the surface, at 
4000. 

The Earth turns on its axis ; though this axis 
is only an imaginary line passing through the 
Earth from pole to pole. This motion is well 



6 THE EARTH. 

represented in the ordinary school globes, and 
may be imitated with an apple or a ball. In 
consequence of this turning motion, called the 
rotation of the Earthy all parts of its surface are 
in succession presented to the sun's rays; and 
since the motion takes place from west to east, 
the Earth always meets or turns to the sun in 
its eastern parts, which gives the appearance of 
the sun's rising in that quarter, the variation to 
the north or south of east being dependent on 
its relative position to the sun at different sea- 
sons of the year. This motion of rotation, called 
the Earth'' s diurnal motion, is completed in about 
24 hours (correctly speaking, 23 hours 56 min- 
utes 4 seconds), which constitutes a natural day. 
The rate of the Earth's rotary motion at the 
equator exceeds 1000 miles an hour; but the 
velocity of rotation diminishes as we recede from 
that line, in accordance with the Earth's dimin- 
ished circumference. 

While the Earth is thus continually turning 
on its axis, it has also a progressive or onward 
motion in its orbit, that is, its path round the sun. 
The length of this orbit has been estimated at 
about 600 millions of miles, and the rate of the 
Earth's motion in its orbit to exceed 68,000 miles 
in an hour, or about 1000 miles in a second. 
The Earth's orbit or path is not perfectly cir- 



THE EARTH. 7 

cular, but elliptical* in consequence of which the 
Earth is not always at the same distance from 
the sun, but its average distance is 95 millions 
of miles. The Earth completes this revolution 
round the sun in 365 days and 6 hours, which 
constitute a year. 

The Earth, while performing its annual course 
round the sun, has not its axis placed at right 
angles with the line it pursues, but in an oblique 
or slanting direction ; the consequence of which 
is, that the earth presents to the action of the sun's 
rays a greater portion of the northern hemisphere 
during one half of the year, and a greater portion 
of the southern hemisphere during the other half 
of the year. The period at which any particular 
portion of the Earth's surface is turned most 
directly towards the sun constitutes mid-summer 
at that particular locality; and it will at the 
same time be mid-winter at the opposite portion 
of the globe. Thus, when it is mid-summer in 
the British Isles, it will be mid-winter at the 
little island of Antipodes, not far from New Zea- 
land : when it is mid-summer in New England, 

* An ellipse is an oval figure so shaped, that the sum of the 
two distances of each point of the curve from two points within, 
called /oci, is always the same. The Sun's place is a. focus of 
each planetary orbit. An ellipse may be drawn with a string, 
two pins, and a pencil. 



b THE EARTH. 

it is mid-winter in the northern part of the Aus- 
tral Ocean. In the figure below, the orbit is 
made much more elliptical than it is in reality, 
and the Sun, which belongs in one of the foci, 
is put at the centre. At each equinox^ a hemis- 
phere is shown which reaches both the poles; 
but at the vernal equinox the illuminated half 
appears, at the autumnal the dark half; the 
globe in the latter case being between the Sun 
and the eye. Observe that the lines n s, repre- 
senting the earth's axis, always remain parallel 
to each other. 



20th IVIaech, 1855. 
4' 




23d Septembee, 1855. 



LATITUDE AND LONGITUDE. 



m. LATITUDE AND LONGITUDE. 

The globe or earth, for the convenience of 
measurement, is divided into degrees of latitude 
and longitude ; these degrees being indicated by 
this sign, °. 

Latitude is marked by lines or circles running 
parallel with the equator, each hemisphere being 
divided into ninety degrees between the equator 
and the north and south poles. The reckoning 
commences from the equator, and is distinguished 
as north and south latitude. The latitude of any 
place is therefore determined by jffcs distance 
north or south of that line. Thus London is in 
north latitude 51^°. The Cape of Good Hope 
is in south latitude 35°. Any place situated on 
or near the equator is said to be in a low lati- 
tude ; any place near the Arctic circle to be in a 
high latitude. Thus, Sierra Leone is in the low 
latitude of 8^-° N., Archangel in the high lati- 
tude of 64^° N. 

Each degree is divided into sixty minutes, 
marked thus,'; the latitude of London being 
51° 30' ; that is, fifty-one degrees, thirty minutes. 
The number of miles comprised in a degree of 
latitude is nearly seventy. 



10 LATITUDE AND LONGITUDE. 

Places situated in the same degree of latitude 
are said to be on the same parallel. Thus, Nor- 
wich and Berlin are on the same parallel of lati- 
tude, about N. lat. 52^ degrees. 

The globe has a further division, also running 
parallel with the equator, marked by four circles^ 
called the Arctic circle^ the Antarctic circle, the 
Tropic of Cancer, and the Tropic of Capricorn, 
The tropics are situated at the distance of 23|-° 
north and south of the equator ; the Arctic and 
Antarctic circles, 23^° from the north and south 
poles, or in north and south latitude 665- de- 
grees. 

These circles divide the earth into five zones, 
or belts, the torrid zone, the two temperate zones, 
and the two frigid zones. The torrid zone, so 
called from the heat of that portion of the earth 
which it includes, extends to 23|^° on each side 
of the equator ; that is, to the tropic of Cancer on 
the north, and the tropic of Capricorn on the 
south, of the equator. This zone is called inter- 
tropical, from its lying between the tropics. The 
northern temperate zone extends from the tropic 
of Cancer to the Arctic circle, and the southern 
temperate zone from the tropic of Capricorn to 
the Antarctic circle; that is, respectively from 
north and south latitude 23^° to north and south 
latitude 66^°. The frigid zones extend from the 



LATITUDE AND LONGITUDE. 11 

Arctic and Antarctic, or polar, circles, to the 
north and south poles ; that is, from north and 
south latitude 66^° to north and south latitude 
90°. They are called frigid, from the cold tem- 
perature which prevails in those regions. 

The Earth's surface is also crossed by imagin- 
ary lines passing from north to south through 
the poles ; these are called meridians. The 
longitude of any place is determined by its dis- 
tance (reckoned in degrees) eastward or west- 
ward from any given meridian. In Britain, 
longitude is calculated from the meridian of 
London (or, more correctly speaking, of the Royal 
Observatory at Greenwich).* 

For the measurement of longitude, the equa- 
tor is divided into 360 parts or degrees ; the same 
division into 360 degrees being maintained in all 
parallels of latitude, though, since the girth or 
circumference of the earth diminishes as we re- 
cede from the equator, degrees of longitude do 
not contain so many miles in high as in low 



* For convenience, the meridian of London is assumed as the 
line from which navigators reckon their longitude, yet in nation- 
al calculations it is customary to make the capital of the country 
the point from which to determine longitude. Thus, in America, 
we have the meridian of AVashington, the Prussians use the 
meridian of Berlin, the Austrians that of Vienna, &c. 



12 LATITUDE AND LONGITUDE. 

latitudes, which will be evident from the follow- 
ing table: — 

LATITUDE. MILES. 

0° 68| 

10° 67^ 

20° 64J 

30° . 59^ 

40° 52J 

50° 44 

60° 341. 

70° 23j 

80° 12" 

90° 

We thus perceive that a degree of longitude at 
the equator contains nearly 69 miles, but in lati- 
tude 80°, only 12 miles, and at the poles it di- 
minishes to nothing. 

Longitude is ordinarily reckoned east and 
west from the meridian of Greenwich to the 
opposite point of the globe's circumference ; 
there being thus 180 degrees of east longitude, 
and 180 degrees of west longitude. All places 
eastward of Greenwich are reckoned as being 
situated in east longitude ; and all places west- 
ward of Greenwich as being situated in west 
longitude. 

Places situated in the same degree of longi- 
tude are said to be on the same meridian* The 
term meridian is used, because the sun will be 

* Derived from the Latin meridieSi mid-day. 



LATITUDE AND LONGITUDE. 13 

at its greatest height, or it will be mid-day^ at the 
same time at all places' in the same longitude. 
Thus, Bordeaux is on the same meridian as 
London, and therefore it will be noon, or mid- 
day, at the same time at both places. It will be 
noon earlier than in London at aU places situ- 
ated to the eastward of that meridian, or in east 
longitude^ and later at aU places situated in ivest 
longitude. The sun will rise rather sooner at 
Berlin, and much later at New York, than in Lon- 
don. At Calcutta, which is situated in east longi- 
tude 88°, it wiU be noon when it is a little after 
six in the morning in London ; and at the Feejee 
Islands, in the Pacific Ocean, which are situated 
nearly at the point where east and west longi- 
tude meet, it wiU be noon, or mid-day, when it 
is midnight in London. The sun is said to be 
on the meridian at mid-day : it is then due south, 
and at its greatest altitude^ or height, for that par- 
ticular day. 

As the earth revolves on its axis once in twenty- 
four hours, the sun passes over one twenty-fourth 
of 360°, or 15°, in one hour. The difference of 
time between two places can be easily calculated 
by dividing the difference of their longitude by 
15. This wiU give the number of hours and 
the fractional part of an hour ; the latter can be 
reduced, if necessary, to minutes and seconds. 



14 l)ISTRIBUTION OF LAND AND WATER. 

This difFerence must of course be added to ob- 
tain the time of a place east of a given meridian ; 
subtracted for a place west of it. 



IV. DISTRIBUTION OF LAND AND WATER. 

The land does not occupy much more than 
one-fourth of the entire surface of the globe, the 
remainder being covered by the waters of the 
ocean. Thus, the extent of the whole surface 
being estimated at nearly 197 million square 
miles, the space occupied by land is considered 
to be about 52 million square miles, and that 
covered by the waters of the ocean about 145 
million square miles. 

The proportion of land is much greater in the 
northern than in the southern hemisphere; it 
having been computed that in the northern 
hemisphere the land occupies about 38 million 
square miles, and the waters of the ocean rather 
above 60 million, whilst in the southern hemi- 
sphere the land has been supposed not to occupy 
quite 14 million square miles, and the waters of 
the ocean to cover an area of about 85 miUion 
square miles. The recent discoveries of large 
tracts of land in the Antarctic regions, the extent 



DISTRIBUTION OF LAND AND WATER. 15 

of which is yet unknown, render the correctness 
of the latter computation more than doubtful. 

The dry land is usually considered under two 
principal heads : continents and islands. 

The term continent has been commonly ap- 
plied to four portions of the earth, and it is cus- 
tomary to speak of the continents of Europe, 
Asia, Africa, and America ; but, more correctly 
speaking, there are only two continents, dis- 
tinguished as the Eastern and Western Conti- 
nents. 

The Eastern Continent, called also the Old 
World — because it has formed the abode of 
civilized man from the earliest period of histori- 
cal records — comprehends Europe, Asia, and 
Africa. The Western Continent, called the 
New World — because it has only been known 
to Europeans since its discovery by Columbus 
in 1492 — includes the whole of America. 

These two vast continents are in fact only 
larger islands, being surrounded on all sides by 
water ; but since large surfaces of land differ in 
their climate and natural productions from islands 
of smaller size, it is desirable to make this dis- 
tinction, and to treat of these two grand divisions 
of the earth as continents. * 

The islands on the earth's surface are of vari- 
ous dimensions, and of various elevations above 



16 DISTRIBUTION OF LAND AND WATER. 

the sea. The immense basin which is occupied 
by the waters of the ocean is apparently greatly 
diversified in its surface ; in some parts deep de- 
pressions or submarine valleys occurring, whilst 
in others partially-immersed mountains rise above 
the waters, forming islands of larger or smaller 
extent, and in some instances mere insulated 
rocks. 

Australia is by far the largest island on the 
face of the globe, its greatest length being about 
2500 miles, and its greatest width about 1800 
mUes. This vast island is sometimes called a 
continent, but is more correctly included among 
the Islands. Australia, in conjunction with 
New Zealand and the numerous smaller islands 
with which the Pacific Ocean is studded, is 
sometimes regarded under the distinct appella- 
tion of Oceanica. 

On referring to the map of the world, we shall 
perceive that the form in which the dry land is 
arranged differs greatly in the Old and New 
.Continents ; in the Old Continent the principal 
extension being from east to west, whilst in the 
New it is from north to south. 

In the Old Continent continuous straight lines 
may be drawn for immense distances from south- 
west to north-east, over vast tracts of dry land, 
without encountering any great expanse of water. 



MOUNTAINS. 17 

Thus, a line drawn from Cape Verd in West- 
ern Africa, crossing the Isthmus of Suez, and 
extending to Quanlin on the borders of the 
Pacific Ocean, (situated a little to the north of 
the Japan isles,) would pass over a tract of dry- 
land no less than 9750 miles in length. The 
New Continent, on the other hand, has its great- 
est length from north to south, extending through 
120 degrees of latitude. 



V. VARIATIONS OF THE SURFACE. 

The dry land is elevated into mountains and 
highlands^ spread forth in plains^ or depressed in- 
to valleys^ all varying in extent and in elevation 
above the level of the sea. 

Mountains are met with in ranges and groups, 
or as isolated mountains. 

Mountain ranges, or continuous ridges of 
mountains, not unfrequently rising to a great 
elevation above the adjacent districts, sometimes 
extend over large tracts of country, the length of 
the principal ridge being usually much greater 
than its width. In many instances we find that 
a general correspondence may be traced between 
the direction of mountain ranges and the form of 
2 



18 



VARIATIONS OF THE SURFACE. 




MOUNTAINS. 



19 



the regions they traverse, as will be evident from 
a reference to the accompanying map, the black 
lines on which indicate the principal mountain 
ranges. 

Thus, the greatest extension of the Old World 
is from east to west, and a vast and nearly con- 
tinuous line of mountains extends across the 
whole continent in that direction. The greatest 
length of the New World is from north to south, 
and in that continent a mighty mountain range 
stretches from its northern to its southern ex- 
tremity. 

The nearly continuous line of mountains which 
may be traced across the whole of the Old Con- 
tinent, from the very shores of the Atlantic to 
those of the Pacific Ocean, commences in West- 
ern Europe ^th the Pyrenees^ with which the 
Sierras, or mountain ranges of Spain, are con- 
nected. The valley of Languedoc forms an 
interruption to the grand chain of mountains, 
intervening as it does between the Pyrenees and 
the comparatively low range of the Cevennes, 
w^hich extend nearly across the south-eastern 
part of France, and which may be considered 
as forming the next prolongation of the line. 
To this range succeeds the mighty moun- 
tain system of the Alps, covering a large ex- 
tent of surface in Switzerland and some of the 



20 VARIATIONS OF THE SURFACE. 

adjacent teiTitories, and containing the most ele- 
vated summits in Europe. The mountains of 
Germany and Bohemia do not attain any great 
altitude ; these are succeeded by the Carpal 
thian mountains, which skirt the north-eastern 
borders of Hungary. From the last range, and 
also from the Alps, mountain branches extend 
into Turkey, where the Balkan range carries the 
great line to the shores of the Euxine or Black 
Sea, and to the confines of Europe. In Asia 
Minor and Syria, it is continued by the ranges 
of Taurus, Libanus, and Anti- Lib anus, and from 
these by the mountains of Armenia and Per- 
sia, including the Elburz range which skirts 
the southern shores of the Caspian Sea, to 
the borders of India. The Caucasian moun- 
tains, situated to the westward of the Caspian 
Sea, appear rather as a detached group. At 
the borders of India we arrive at a grand 
mountain knot, the Hindoo Koh or Coosh, from 
which mountain ranges diverge to the north 
and to the south, as well as to the east and west. 
The grand line is prolonged to the eastward by 
the Kuenlun and the Himalaya mountains, the 
latter stupendous range, which separates Hindo- 
stan from Tibet, containing the loftiest known 
summits on the face of the globe. The Himalaya 
mountains take a south-easterly course, and ter- 



MOUNTAINS. 21 

minate at the river Brahmapootra, whence the 
line is continued by ranges of mountains hitherto 
little explored, and finds its termination in the 
mountains of Chitia, which carry it to the shores 
of the Pacific Ocean. The Kuenlun mountains 
skirt the north of Tibet and are prolonged by the 
Kliin-g'an range, which, turning northward, is 
again prolonged by other ranges, running in a line 
nearly parallel with the eastern coast of Asia, and 
extending almost to its most northerly limits. 

The vast mountain system which extends from 
the northern to the southern extremity of the 
New World, presents a far more striking instance 
of the correspondence between the direction of 
mountain ranges and the regions they traverse. 
The Rocky Mountains extend from the borders 
of the Arctic Seas to the Isthmus of Panama, 
their general course agreeing very closely with 
that of the western coast line of North America. 
This vast range becomes twice depressed in Cen- 
tral America, but soon regains more than its 
former height, and under the name of the Andes 
extends along the whole of Western South 
America, its direction corresponding very nearly 
with that of the coast. The Andes contain a 
vast assemblage of elevated summits, a great 
number of which are covered with perpetual 
snow, although some of them are situated in the 



22 VARIATIONS OF THE SURFACE. 

hottest regions of the globe. Numerous active 
volcanoes also occur among the Andes. As 
they approach the southern extremity of the con- 
tinent, these mountains lose their great elevation, 
and finally terminate in Cape Horn, 1860 feet 
above the level of the sea. The course of the 
Alleghany mountains corresponds nearly with 
that of the eastern coast of the United States. 

The character of general correspondence be- 
tween the direction of mountain ranges and the 
form of the regions they traverse, is often very 
observable in smaller portions of land, such as 
peninsulas and islands. Thus, the form of Italy 
corresponds closely with that of the direction 
taken by the Apennines, which extend through 
the whole of that peninsula. The form of Scan- 
dinavia (Sweden and Norway) agrees with the 
direction of the Dofrefeld mountains, which tra- 
verse that territory from north to south. Among 
islands, Corsica, Madagascar, Cuba, and Jamai- 
ca, afford striking instances of the correspondence 
of mountain ranges w^ith the form of the land 
along which they extend. 

Mountain ranges present some of the grandest 
natural scenes on the face of the globe. The form 
of ridges and summits is much influenced by the 
nature of the rocks of which they are composed. 
In some regions, the mountain tops are rounded, 



MOUNTAINS. 23 

like the limestone summits among the Apen- 
nines ; in others, serrated or saw-shaped, like the 
slaty Sierras of Spain ; in others, they rise in 
peaks or horns, like Mont Blanc and *Finster- 
aar-horn in the Alps ; in others, in perpendicular 
walls 1000 or 2000 feet in height, like some por- 
tions of f Mont Cervin in the same range ; or like 
natural castles, as in Mount Athos, in Greece ; 
or in gigantic dome-shaped masses, like Chim- 
borazo in the Andes. One very striking feature 
in elevated mountain ranges consists of the vast 
surface of snow which everywhere meets the eye, 
particularly in such mighty mountain ranges as 
the Himalaya and Andes. Mountain ranges are 
usually furrowed by deep valleys ; and in some 
parts these valleys are filled with vast accumu- 
lations of ice and snow, called glaciers^ which 
often assume the most fantastic forms, or spread 
forth like lakes or seas of ice, sometimes having 
a thickness of nearly 600 feet. J 

Mountain branches^ or ridges, usually of in- 
ferior elevation, frequently diverge or branch off 
from the central line of a mountain range, 



* In the Bernese Alps. t In tlie Pennine Alps. 

t For an admirable description of the glaciers of the Old 
World, the reader is referred to Rollo in Switzerland, a book 
which may be perused with equal profit by young and old. 



24 VARIATIONS OF THE SURFACE. 

sometimes running almost parallel with the 
principal ridge, like the Jura * range, which 
branches off from the central line of the Alps ; 
or else diverging from it nearly at right angles, 
like the Apennines, from the same grand moun- 
tain range. These are termed lateral or side 
branches^ and sometimes transverse branches. 
From these lateral branches, smaller branches or 
spurs again extend, constituting hills^ and the 
latter usually diminish in height until they are 
lost in the plains. 

Detached or isolated mountains are usually of 
volcanic origin. In many instances they contain 
active volcanoes, and they sometimes attain a 
great elevation. Thus Mount Etna in Sicily 
has the altitude of 10,880 feet above the level of 
the sea, the peak of Teneriffe in the Canary 
Islands that of 12,200, and Mount Ararat that of 
17,262 feet. 

The loftiest summits are usually met with in 
extensive mountain ranges : thus, the most ele- 
vated summits in Great Britain occur in the 
mountain ranges of Scotland ; those of Europe, 
among the Alps ; those of Asia in the Himalaya 
Mountains ; and those of America in the Andes : 
as may be observed by a reference to the follow- 

* Between Neufchatel and Lake Geneva.^ 



MOUNTAINS. 25 

ing table of the height in feet above the level of 
the sea, of the most remarkable mountains on 
the earth's surface. 

EUROPE. 

Feet. 

Mont Blanc, Alps 15,750 

Monte Rosa, Alps 15,150 

Mulahacen, Sierra Nevada, Spain .... 11,650 

Pic Nethou, Pyrenees 11,168 

Mont Perdu, ditto 10,950 

Etna, volcano, Sicily 10,880 

Argentaro, Balkan 10,000 

Corno, Apennines 9,250 

Skagesloestinden, Norway . ... 8,100 

Lomnitz, Carpathians 8,750 

Parnassus, Greece 8,000 

Schneeliatten, Norway 7,549 

Mont d'Or, Auvergne 6,220 

Helca, volcano, Iceland 5,210 

Vesuvius, volcano, Italy . . .... 3,900 

BRITISH ISLES. 

Ben Nevis, Inverness-shire 4,368 

Snowdon, Caernarvonshire 3,571 

McGillyc^ddy's Reeks, co. Kerry .... 3,410 

Helvellyn, Cumberland 3,055 

Kinderscout, highest point of the Peak of Derbyshire . 1,981 

Beachy Head, Sussex 564 

ASIA. 

Kunchin-ginga, Himalaya 28,174 

Dhawala-giri, ditto (about) .... 28,000 
Juwahir, ditto 25,770 



26 VARIATIONS OF THE SURFACE 

Feet. 

Elburz, Caucasus ... . . 18,400 

Ararat, or Agri-dagh, Armenia . . . . 17,262 

Hermon, Syria 10,000 

Sinai, Arabia ... .... 9,300 

AFRICA. 

Kilmand-Jaro, Zanguebar 20,000 

Abba Tared, Abyssinia 15,000 

Cameroons, Biafra ..... . 13,000 

Peak, Teneriffe, volcano 12,200 

Spitz Kopf, Cape of Good Hope .... 10,000 

Table Mount, ditto S,500 

NORTH AMERICA. 

Mount St. Elias, volcano . ... . 17,860 

Popocatepetl, Mexico, ditto . . . • . 17,716 

Fremont's Peak, Rocky Mountains . . . 13,560 

Black Mountain, AUeghanies, N. Carolina . . . 6,476 

Mount Washington, White Mountains, N. H. . . 6,285 

SOUTH AMERICA. 

Lirima, Andes 24,000 to 25,000 

Aconcagua, Andes . . . . . . 28,907 

Sahama, ditto . 22,350 

Chimborazo, ditto 21,415 

Sorata, ditto . * 21,286 

Illimani, ditto . . . . . . . 21,145 

Roraima, Guiana 7,450 

Itambe, Brazil 5,960 

Cape Horn, Tierra del Fuego 1,860 

* According to Johnston and Petermann. 



TABLE-LANDS. 27 

OCEANICA. 

Mowna Roa, Hawaii, volcano 16,000 

Erebus, South Victoria Land, volcano . . . 12,400 

Peak, Tahiti . . ' 10 875 

Egmont, New Zealand ...... 9,000 

Sea- View Hill, Australia 6,500 

Elevated plains or highlands^ called plateaus or 
table-lands^ occur in various parts of the earth's 
surface. They sometimes rise abruptly and 
almost perpendicularly from the lower plains, 
and it is in consequence of this table-like form 
that the appellation of table-land has been 
adopted, though the term is applied to any 
plains of considerable elevation above the level 
of the sea, even though they bear no resem- 
blance to the table-like form; some table-lands 
or plateaus being, on the contrary, situated be- 
tween parallel mountain ranges, the mountains 
which support them often towering to great 
heights above these elevated plains. 

The most considerable plateau or table-land 
of Europe occurs in Central Spain, which has a 
general elevation of 2000 feet above the sea level. 
The plateau or table-land of Mexico has an ele- 
vation of about 7000 feet above the sea. The 
table-land of Quito, w^hich is situated between 
two parallel ridges of the Andes, has an eleva- 
tion of 9000 feet above the sea, whilst around it 



28 VARIATIONS OF THE SURFACE. 

rises a vast assemblage of elevated summits, no 
less than eleven snow-capped mountains being 
visible from that .plain. The most remarkable 
table-land on the surface of the globe occupies a 
large space of Central Asia, including the desert 
tracts of Gobi and Shamo and the elevated 
region of Tibet, the latter of which has an 
elevation of 15,000 feet above the level of the 
sea. 

Plains or lowlands of greater or less extent, 
presenting comparatively small undulations on 
their surface, and rising in no part to any great 
elevation, are met with in most parts of the 
globe. A large plain or lowland occupies a con- 
siderable space in Europe, commencing on the 
borders of the North Sea, in the low dis- 
tricts of the Netherlands, and extending through 
Prussia and Poland into Russia, to the base of 
the Ural Mountains, and forming in the latter 
country an almost uninterrupted plain from the 
shores of the Frozen Ocean to those of the Black 
and Caspian Seas. In this vast expanse the sur- 
face is scarcely broken by any eminence except 
the low range of the Valdai hills, between Mos- 
cow and Toropetz, which in no part exceeds the 
height of 1200 feet above the level of the sea. 
This extensive plain is divided by the Uralian 
Mountains from one of yet larger extent, which 



PLAINS. 29 

forms the great lowland of Northern Asia. The 
Russian Steppes (according to Koch) are open 
woodless tracts, covered with tall herbaceous 
plants. 

One of the most remarkable lowlands on the 
earth's surface consists of the vast tract of barren 
sand which occupies the large portion of North- 
ern Africa, called the Sahara or Great Desert^ and 
which extends from the borders of the Atlantic 
Ocean to the valley of the Nile, its length being 
about 2470 miles, and its breadth about 900 miles. 
It consists chiefly of low rocky hills, and an almost 
boundless extent of moving sand, unrefreshed by 
a drop of rain, and parched and pulverized by 
the intense heat of a tropical sun. In some few 
spots, where springs of water rise to the surface, 
and admit of the growth of vegetation, a verdant 
oasis or wady^ of greater or less extent, varies 
the otherw^ise arid and dreary surface of this 
enormous desert, appearing like an island in the 
midst of an ocean of sand. 

America contains some lowlands of vast ex- 
tent. Wide-spreading savannahs^ or plains, oc- 
cupy a large tract of country, forming the basin, 
or valley, of the river Mississippi, situated to the 
west of the Alleghany Mountains. A consider- 
able portion of this great lowland is remarkably 
level, and subject to annual inundations from 



30 VARIATIONS OF THE SURFACE. 

the mighty stream by which it is traversed. 
Other parts consist of dense forests alternating 
with prairies^ or extensive natural meadows, 
abounding in wild animals. 

In South America three remarkable plains or 
lowlands occur. The basin of the river Oronoco 
forms the most northern ; these plains are usually 
called llanos; the second great plain is that 
which is traversed by the mighty river Ama- 
zon, and which extends from the shores of the 
Atlantic to the base of the Andes, having a 
gradual slope, and being in many parts covered 
with almost impenetrable forests, and in others 
with luxuriant herbage. These plains are dis- 
tinguished as selvas. The third great low- 
land of South America, which includes the 
vast plains of Buenos Ayres, and extends to the 
•cheerless wastes of Patagonia, forms the basin 
of the rivers Paraguay and La Plata. These 
plains are usually termed pampas. 

Valleys are of three kinds : — Principal val- 
leys ; lateral or tranverse valleys; and subordi- 
nate valleys. 

Principal valleys are usually valleys of large 
dimensions, enclosed between extensive parallel 
ranges of mountains. To this class belongs the 
Valais, or Valley of the Rhone. This valley is bor- 
dered on the south by the Pennine Alps, among 



VALLEYS. 31 

which we meet with Mont Blanc and some of 
the other most elevated mountain peaks in 
Europe ; and on the north it is bordered by the 
Jura and the Swiss Alps. 

Lateral valleys^ or transverse valleys^ are so 
termed, because they are situated among and 
formed by the lateral or transverse branches of 
mountain ranges, and their size and general 
arrangement therefore depend on the magnitude 
and direction of the mountains among which 
they occur. 

Subordinate^ valleys^ as the name implies, are 
valleys of subordinate or smaller size, which are 
formed by the spurs or minor branches of 
mountain ranges, or which are situated among 
hills. 

Some valleys are basin-shaped, or of a circular 
form, being surrounded by a girdle of mountains, 
with the exception of one small outlet, which 
allows of the escape of the superabundant 
waters. Such valleys appear to have formed 
the beds of lakes at some previous period, the 
waters of which having been drained off through 
the small gorge or outlet, the lake has been con- 
verted into a fertile valley. The beautiful valley 
of Cashmere presents an example of a basin- 
shaped valley. 

When valleys are narrow and difficult of 



32 VARIATIONS OF THE SURFACE. 

access, they are termed ravines^ glens, dells, de- 
files, gorges, gullies, passes or ports. Narrow 
valleys of this description are of frequent occur- 
rence among steep mountains, and often present 
scenes of great beauty and grandeur. They 
usually form the routes by which mountain 
ranges are crossed, and hence they are called 
ports in the Pyrenees, and passes in the Alps and 
various other mountain ranges. As they are not 
situated at the highest point, but just below the 
head or summit of the mountain, they are called 
cols or necks in the Alps of Europe. They fre- 
quently form the beds of rivers which take their 
rise amid the snows of mountain regions. 

The valleys and plains to which our attention 
has hitherto been directed, though low in eleva- 
tion as compared with hills and mountains, are 
all more or less above the level of the sea, which 
latter forms the standard by which all the undu- 
lations on the earth's surface are measured. In 
Central Asia a large tract of country exists which 
is commonly supposed to be depressed below the 
sea level, though the fact is denied by high 
authority. This extensive area includes the 
Caspian Sea and the Sea or Lake of Aral. 



33 



VI. GEOLOGY. 

Geology consists of an inquiry into the na- 
ture and arrangement of the various rocks and 
other substances at or near the surface of the 
earth. 

The portion of the earth which is accessible to 
man's observation is termed the earth^ crusty 
though this forms but a very small part of the 
whole globe, for the deepest mine hitherto ex- 
plored scarcely penetrates more than half a mile 
into the interior of the earth, and the inequalities 
on its surface arising from mountains and val- 
leys have been well likened to the roughness on 
the rind of an orange, as compared with the 
general mass. 

An examination of the earth's crust shows us 
that it is formed of numerous beds or strata of 
rocks, some of limestone^ some of sandstone^ some 
of clay ; some very hard, others soft and crum- 
bling and readily worn away by the action of 
running streams or ^he waves of the ocean. 
The greater number of these beds contain organic 
remains^ that is, the remains of animals and 
plants, which are termed fossils. Among these 
the most numerous are the remains of marine 
3 



34 . GEOLOGY. 

animals ; in some instances, shells and corals 
occur in such abundance as to form the principal 
part of extensive beds. Every part of the earth 
exhibits similar or nearly similar formations ; 
and not only are marine fossils met with in the 
interior of continents and -at great elevations 
above the sea, but a vast variety of plants, corals, 
shells, fish, reptiles, &c. &c., are met with in a 
fossil state, of species dissimilar to any at pres- 
ent on the land or in the waters. 

Besides rocks, we meet with earthy formations 
on the earth's surface. These include such loose 
materials as are disintegrated or worn away from 
rocks, and form, when combined with decayed 
animal and vegetable matter, or humus, the soil 
of meadow and arable lands, and, generally 
speaking, all beds which are not consolidated, or 
hardened. Water-worn pebbles, that is, frag- 
ments of rocks rounded by friction and the 
action of water, are of frequent occurrence, form- 
ing gravel in the beds of rivers, &c., and shingles 
on the sea-shore. When of very large size, they 
are termed boulders. 

When rounded pebblest become cemented to- 
gether by lime or any other material, so as to 
form a solid rock, the mass is called conglomer- 
ate, and sometimes pudding-stone. When angu- 



EARTHS. 35 

lar fragments are thus cemented together, the 
term breccia is substituted. 

The most abundant materials or earths of 
which rocks are composed are, 1, silica^ or Jiint; 
2, lime ; and 3, alumina^ or clay. 

Silica, or silex, is very universally diffused over 
the earth's surface. It is found almost pure in 
quartz, flint, opal, chalcedony, rock crystal, and 
in the flinty sand of the sea-shore. Water passes 
freely through sand ; and, accordingly, sandy 
tracts do not retain water so as to promote vege- 
tation, and they are therefore usually barren ; of 
which the Sahara presents a striking example. 

Lime is also a very generally distributed earth, 
and is usually found in the form of carbonate of 
lime. Under the several names of marble, lime- 
stone, oolite, and chalk, it constitutes mountains, 
and even ranges of mountains. 

Alumina is likewise a very abundant earth, 
and of great importance to mankind. It enters 
largely into the clayey or argillaceous earths. 
It forms part of various kinds of rocks, and 
its special utility arises from its property of not 
permitting water to pass through its substance 
— a property which renders it of inestimable 
value, both for natural and artificial reservoirs 
of water. 

The beds or layers of rocks which form the 



36 GEOLOGY. 

crust of the earth are divided into stratified and 
unstratified. 

1. Stratified or sedimentary rocks are such as 
give evidence of having been formed by suc- 
cessive deposits of sediment in water. They 
are called stratified, because the materials of 
which they are composed appear to have been 
deposited in successive strata or layers; they 
are also called aqueous^ because this appears to 
have been effected by the agency oi water ; they 
include sandstones or freestones^ limestones^ clays, 
&c. 

Stratified rocks being formed by successive 
deposits of layers of sedimentary matter by 
means of water, it is evident that these materials 
must be derived from some source, and in many 
instances this may be traced to the disintegration 
or crumbling away of older rocks. Thus gneiss 
appears to be formed by the disintegration of 
granite, conglomerate by that of various kinds of 
rocks. 

Although all the different kinds of stratified 
rocks do not occur in every part of the earth's 
crust, they are found to form a regular series, 
and those which are of more recent formation 
have never been met with under those which are 
considered as more ancient. Most of the stratified 
rocks contain fossils ; and since each group con- 



STRATIFIED ROCKS. 



^ 



tains a certain number of fossils peculiar to itself, 
it is by means of these organic remains that the 
relative ages of the different strata have been 
determined. 

But although the lowest stratified rocks are 
more ancient than those which have been de- 
posited above them, the layers or beds do not 
always retain a horizontal position. /Were such 
the case, it could only be by means of deep cut- 
tings that we should arrive at the older strata ; 
we, however, find, that owing to some convul- 
sions of the earth, stratified rocks, and in some in- 
stances, whole series of stratified rocks have been 
thrown out of their original horizontal position, 
and thus the various beds crop out or come 
to the surface, as in the accompanying cut, 
where we perceive that no less than five differ- 
ent kinds of rock come to the surface. 




Not only is facility thus afforded us to become 
acquainted with the nature of the lower rocks, 
but many of the most valuable products of the 
earth are by this means rendered more accessible 
to man. 



38 GEOLOGY. 

2. Unstratifiedrocks are such as appear to be of 
igneous origin ; that is, to have been formed by 
the action oifire or intense heat; they are called 
unstratified, because, instead of having been de- 
posited in successive layers, like the stratified 
rocks, they seem to have been formed by the 
fusion or melting of the materials of which they 
are composed, and the subsequent cooling and 
hardening of the melted matter into one great 
mass. Granite^ basalt^ lava, &c., belong to this 
class of rocks. 

Unstratified rocks may be divided into three 
classes: — 1. Plutonic; 2. Trap; 3. Volcanic. 

Plutonic rocks are rocks which appear to have 
been formed at a considerable depth in the in- 
terior of the earth by the agency of heat, and in 
consequence of their having cooled under the pres- 
sure of superincumbent, or over-lying- rocks, to 
have become greatly compressed and hardened. 
The principal rock of this class is granite, which 
is a very universally diffused rock, though in 
very many parts of the earth it is concealed from 
our view by the stratified rocks which rest upon 
it. In some parts, granite veins or branches ex- 
tend upwards into the stratified rocks. Granite 
occurs in all of the New England States, but the 
purest and most easily wrought is found at 
Quincy and Rockport in Massachusetts. 



UNSTRATIFIED ROCKS. 39 

Trap rocks are formations which are consider- 
ed to be the products of volcanoes which have 
been long extinct These rocks, like the Plutonic, 
are supposed to have been in a state of fusion, 
but to have cooled down under the pressure of 
deep water ^ probably of a profound ocean. Basalt 
is one of the most abundant rocks of this class. 
It sometimes occurs in tabular masses, but more 
frequently in regular columns, usually called 
basaltic columns. The Gianfs Causeway, in the 
north of Ireland, presents a remarkable instance 
of a formation of this kind. Trap dikes are 
masses of trap which have forced their w^ay into 
or through other rocks, and are sometimes of 
great extent. 

Volcanic rocks are less compact and less hard- 
ened than either plutonic or trap rocks, which is 
supposed to be owing to their having cooled in 
the open air. The principal volcanic rocks are, 
tufa or calc tuff, pumice-stone, and obsidian. 
Loose sand, scorice or cinders, and ashes, are also 
ejected from the craters or mouths of volcanoes, 
and some volcanoes pour forth streams of muddy 
water, whilst all emit volumes of gaseous matter 
and steam. 

The regions where volcanic action is at present 
displayed in the greatest energy include Mount 
Vesuvius and Mount Etna, and the adjacent seas; 



40 GEOLOGY. 

the islands of the Indian Archipelago; Central 
America and the Andes ; some of the islands of 
Oceanica; Iceland and Kamtschatka^ in the cold 
regions of the north ; and South Victoria Land, 
amid the perpetual snows of the southern polar 
regions. 

Terrific as are the effects sometimes produced 
by volcanic eruptions, there seems reason to con- 
clude that in many instances they may rescue 
the districts where they occur from the yet more 
destructive visitations of earthquakes. For it 
appears that the melted matter in the interior of 
the earth, being enlarged in its volume by the 
action of internal heat, strives to force its way 
through the rocks which form the earth's crust ; 
but on encountering the outlet afforded it by the 
crater of a volcano, this melted matter pours 
forth on the surface of the ground. The melted 
matter or lava ejected by the volcano of Skaptar 
Yokul, in Iceland, in the year 1783, was of im- 
mense volume. Two streams of lava flowed in 
opposite directions, the width of one stream 
being about twelve or fifteen miles, its depth 
about one hundred feet, and it extended to about 
fifty miles from the mouth of the volcano. The 
second stream was of equal depth, but not of so 
£^eat width, nor did it extend beyond forty miles. 
Had this mighty mass of melted matter not found 



EARTHQUAKES. 41 

a vent, we may well suppose that it might have 
shattered the rocks to atoms, and given rise to 
the most fearful earthquakes. And in fact it fre- 
quently happens, that in volcanic regions, earth- 
quakes cease at the very moment that eruptions 
commence from adjacent volcanoes, and occasion- 
ally even from volcanoes comparatively remote 
from the convulsion. It thus appears that in 
certain portions of the earth's crust, underground 
communication must extend to considerable dis- 
tances. This is strikingly displayed in the 
Andes, and a wide extent of country at their 
base. 

The effects produced by earthquakes are some- 
times very remarkable, convulsions of this kind 
occasionally agitating immense tracts of country, 
shattering and displacing rocks, and even perma- 
nently raising continuous tracts of land above 
their former level, or causing the depression of 
others ; thus effecting great alterations in the sur- 
face of the countries where they occur. 

Earthquakes of great severity sometimes occur 
in regions remote from any active volcano ; of 
this the tremendous convulsion which took place 
at Lisbon in the year 1755 forms an instance. 
On that occasion the agitation of the earth's 
crust extended to the British Isles, and even to 
the West Indies and some parts of North Ameri- 



42 



GEOLOGY. 



ca. Slight tremors of the earth are occasionally 
felt in all parts of the globe. 

Extinct volcanoes occur in various parts of 
the earth's surface ; and in such cases we may 
infer, that though at some former period earth- 
quakes and volcanic eruptions may have taken 
place in those localities, these have now ceased, 
and the melted mass has cooled down and 
formed a solid rock. 

Igneous rocks have in many cases forced their 
way up through stratified rocks, forming what 
are termed intrusive rocks, because they have in- 
truded into the region of rocks of another class. 
These igneous formations, whilst still in a molten 
state and intensely hot, coming in contact with 
the aqueous or stratified rocks, have usually 
changed the character of those portions immedi- 
ately near them, thus forming what are called 
metamorphic or transformed rocks. By such 
means limestone rocks have become transformed 
into crystalline marble. 

The effects produced at remote periods by 
violent convulsions of the earth may also be 
traced by the dislocations or faults to which they 
have given rise. A dislocation or fault is so 
named because any bed or stratum of rock 
where it occurs has been rent asunder and dislo- 
cated or displaced, so that one portion is either 



METALLIC VEINS. 43 

raised above or depressed below its former level : 
the stratum being therefore no longer entire and 
continuous, an interruption ox fault takes place. 

As sandstone and limestone rocks permit 
water to percolate or pass through their substance, 
which clay does not, these dislocations or faults 
are of great importance in the natural world, the 
clay strata frequently, in consequence of their 
altered position, arresting the water and causing 
it, instead of remaining concealed beneath the 
surface in an extended sheet, to gush out in the 
form of a spring at the point where the disloca- 
tion has occurred. The fissures or crevices where 
these displacements have taken place are not 
unfrequently found filled with clay and other 
materials, which arrest the water in its progress. 

In some localities fissures are found to con- 
tain metallic substances, and are then distinguish- 
ed as metallic veins. Such fissures are fi-equent- 
ly found partially filled with calcareous spar or 
crystallized carbonate of lime, which forms the 
matrix or covering in which the metals are in- 
closed. 

Metallic or metalliferous veins are supposed to 
have been partly filled by mechanical means, that 
is, by particles of metallic substances being con- 
veyed into them by the action of water or some 
other power ; and partly by chemical action, that 



44 GEOLOGY. 

is, by sublimation, or fumes rising' from below, 
causing deposits to take place in these fissures. 
The rich lodes or rftetalliferous veins of Corn- 
wall in England occur in fissures, more than one 
dislocation having in many instances apparently 
taken place. 

Some metallic deposits appear to occur in situ- 
ations where igneous rocks have intruded them- 
selves into stratified rocks, and converted them 
into crystalline rocks. Gold is supposed to be 
found almost invariably under such circum- 
stances. Such appears to be the case in the rich 
deposits near the Ural mountains in Asiatic Rus- 
sia ; as also in California and in Australia ; in 
all which places it is met with in quartz. It is in 
pebbles and sand of the same rock that it occurs 
in the beds of rivers, and in some cases is found 
spread over a large extent of country. 

Copper, though frequently met with in veins, 
is also found in extensive masses or beds, inter- 
posed between layers of rock. The same re- 
mark applies to tin, lead, and silver. Iron is a 
very generally diffused metal, and is met with in 
beds, and also in nodules, or rounded masses, 
which occur in great abundance among some 
kinds of rocks. 



45 



Vn. THE WATERS OF THE GLOBE. 

The waters of the globe may be considered 
under four heads; — 1. Spring's; 2. Rivers; 3. 
Lakes; 4. The Ocean. 

• Spring's, or natural fountains of water, take 
their rise from reservoirs, or sheets of water, 
stored beneath the surface of the ground. A 
sheet or body of water has a tendency to main- 
tain the same level surface, or to rise to the 
same height, wherever it may spread ; the height 
to which a spring will rise depends therefore on 
that of the surface of the reservoir of water from 
which it is supplied. If the internal reservoir of 
water be situated in a hill, and the spring should 
gush out in a valley, the water may rise to a con- 
siderable height above the surface of the ground, 
and form a natural fountain ; but, on the other 
hand, if the reservoir be situated at some depth 
below the surface of the ground, the water 
may never reach the surface, and the aid of 
a bucket or a pump may be required to obtain 
water from such a source. 

These internal reservoirs of water are in great 
measure supplied by moisture derived from rain, 
snow, mist, and dew. This atmospheric water 
enters the earth through porous rocks, or by 



46 THE WATERS OF THE GLOBE. 

means of fissures, and continues to sink until 
arrested in its progress into the interior of the 
earth by rocks such as clay, which will not per- 
mit water to pass, or else by faults, which check 
it from spreading into a wider sheet. The water 
then will gush forth as a spring of greater or less 
size, according to the supplies it may have re- 
ceived. The peaks or pointed summits of moun- 
tains, owing to the small surface they present for 
collecting the rain, snow, or dew, are not favor- 
able for the formation of copious springs. 

All springs contain a certain proportion of air 
and gas, and also some solid matter, usually in 
the form of salts. When this does not exceed a 
three-thousandth part of the whole, they are 
termed soft ; but if the solid contents exceed this 
proportion, the water becomes hard. When 
these salts are in great abundance, the water 
becomes wholly unfit for domestic use, and 
mineral springs are formed. Such springs are 
found in Worcestershire in England, and in Amer- 
ica, throughout the states of Ohio, Kentucky, and 
New York. The springs in Onondaga county, 
N. Y., are the most valuable, and have long been 
worked. 

Medicinal springs contain in addition to com- 
mon salt, sulphate of soda and sulphate of mag- 
nesia, commonly known as Glauber's and Epsom 



THE WATERS OF THE GLOBE. 47 

salts. The Cheltenham springs in England are 
an example of these. 

Mineral springs may be divided into six 
classes: 1. Acidulous; 2. Chalybeate; 3. Sulphu- 
reous; 4. Saline; 5. Calcareous; 6. Siliceous. 

Acidulous waters present a sparkling appear- 
ance, which arises from their containing carbonic 
acid gas. Of this, the pleasant beverage called 
Seltzer water forms an example. Carbonic acid 
gas has the property of rendering soluble in 
water the oxide of iron and various other min- 
eral substances, and therefore these springs 
usually contain some earthy or saline ingredi- 
ents. The springs at Saratoga belong to this 
class. 

Chalybeate springs^ properly so called, are such 
as hold in solution either the carbonate or sul- 
phate of iron. A small spring of this description 
occurs near Brighton in England. 

Sulphureous springs contain sulphur either in 
the form of sulphuretted hydrogen^ as the springs 
of Avon, N. Y., or the numerous sulphur springs 
of Virginia ; or in that of sulphate of lime^ like 
the springs of Baden, near Vienna. 

Saline springs are of two kinds, brine springs 
and medicinal salt springs. Brine springs con- 
tain, besides some other mineral ingredients, a 
greater or less proportion of chloride of sodium^ or 



48 SPRINGS. 

common salt, some springs yielding one-fourth of 
their weight in salt. 

Calcareous springs, or springs highly charged 
with calcareous matter, are met with in limestone 
rocks, from which they derive their calcareous 
ingredients. Water has the property of dissolv- 
ing the calcareous rocks over which it flows or 
through which it filters, and of again depositing 
it, so as to form as the water evaporates an in- 
crustation and in process of time a solid rock. 
The Dropping Well at Knaresborough affords an 
instance of such a spring. The water falls in the 
form of a shower from a projecting ledge of rock, 
and if plants, or shells, or the bones of animals 
are placed so as to allow the water to fall on them, 
they become embedded in the tufa or travertine, 
as it is called, and apparently converted into 
stone, in which state they may be permanently 
preserved. And hence these springs are usually 
termed petrifying or mineralizing springs. 

In some instances when water percolates or 
filters through limestone rocks into cavernous 
recesses, very beautiful formations called stalac- 
tites and stalagmites are met with ; the stalactites 
bemg suspended from the ceiling of the cavern 
like icicles of stone, and the stalagmites being 
formed by successive deposits on the ground 
and rising in aU varieties of form from the floor. 



SPRINGS. 49 

Stalactites and stalagmites in some caverns meet 
and unite, presenting the appearance of columns 
supporting an edifice. Travellers who have 
visited Mammoth Cave in Kentucky describe 
the splendor of the natural haUs and the vast 
pillars as they glitter in the torch-light. 

Siliceous springs are so named from holding 
silica ox flint in solution. These springs are aU 
hot or thermal^ as well as mineral springs. The 
most remarkable springs of this class are the 
Geysers of Iceland. 

Thermal or hot springs are met with in all 
parts of the globe. They may be arranged in 
two classes : 1. Those which owe their high tem- 
perature to the natural heat of the earth at cer- 
tain depths ; and 2. Those which derive it from 
volcanic action. 

It has been found that on penetrating into the 
earth below the depth of 100 feet, an increase of 
temperature takes place, both in solid rocks and 
in internal reservoirs of water, the increase being 
at the rate of about one degree of Fahrenheit's 
thermometer in 45 feet. And, accordingly, 
springs which have their sources at greater 
depths possess a higher temperature than those 
which derive their s,upplies nearer the surface. 
This has been proved by water obtained from 
4 



50 THE WATERS OF THE GLOBE. 

Artesian wells at various depths. One of these 
near Paris i^ 1800 feet deep. The water as 
it rises to the surface is 50 degrees above the 
freezing point. At this rate of increase in the tem- 
perature, all water is in a boiling state two miles 
below the surface ; at a depth of ten miles, if the 
temperature increases at the same rate, (and we 
have no reason to think that it does not,) metals 
are at a red heat ; at thirty, all known substances 
must be in a state of fusion. 

The hottest springs are those situated near 
active volcanoes. Among these the Geysers of 
Iceland hold a prominent place, their temperature 
being rather above the point of boiling water. 
Some springs connected with extinct volcanoes 
have a very high temperature. Many of these 
are found in the south of France. 

Bituminous or pertroleum springs^ that is, 
springs charged with bitumen^ petroleum^ naphtha^ 
asphaltum, &c., are of common occurrence in 
volcanic districts, or in districts where traces of 
igneous action are distinctly observable. 

RIVERS. 

The sources or first waters of rivers are usually 
derived from springs, or from the melting of 



RIVERS. 51 

accumulations of snow. They do not therefore 
receive their largest supplies from the actual 
summits of mountains, for copious springs are 
rarely met with in such situations, nor are glaciers 
formed on the highest points of mountains, but 
more usually on the declivities or slopes of the 
upper mountain valleys. It is accordingly in 
the latter localities that many of the largest 
rivers take their rise. Thus the Rhone has its 
source in the glaciers of the Alps, at the elevation 
of 10,000 feet above the level of the sea. 

It not unfrequently happens that several rivers 
take their rise in one mountain ridge, some of the 
rivers flowing in one direction, and others taking 
an opposite course. This ridge is termed the 
ivater-shed. The mountainous districts of West- 
moreland form the principal water-shed of the 
north of England. The Eden flows in one 
direction, the Tyne and Tees in another, the 
Ouse in a third, &c. The chief water-shed in 
Europe is formed by the Alpine system, and its 
prolongation into Germany. Thus the Rhine, 
the Rhone, and the Danube, all take their rise in 
the Alps, the first discharging itself into the Ger- 
man Ocean, the second into the Mediterranean, 
and the third into the Black Sea. In Eastern 
Europe the water-shed is formed by the low 
ridge of the Valdai Hills, not more than 1200 



52 RIVERS. 

feet above the level of the sea. From this the 
Volga flows, which pours its waters into the 
Caspian Sea, the Dwina,* which falls into the 
Baltic, and the Dnieper, which enters the Black 
Sea. 

Thus the Appalachian Chain, including the 
Cumberland and Alleghany Mountains and the 
Blue Ridge, is the chief water-shed of the eastern 
United States. It sends the James, the Rap- 
pahannock, the Santee and the Savannah to the 
Atlantic, the Cumberland, the Monongahela,, 
the Kentucky and the Tennessee to the Ohio. 

The portion of country through the course of 
which a river lies, and which is drained by it 
and its tributary streams, is called its basin. 
The extent of the basin of the Thames is esti- 
mated at about 5000 square miles. The area 
drained by the river Thames and its tributary 
streams is very small, compared with that drained 
by some of the great rivers of the globe. The 
largest river basin in Europe, as will be observed 
in the following table, is that of the Volga, the 
largest in the world that of the Amazon. 



* On many American mapa the name of this river is spelt 
Duna. The pupil must not confound it with another river of the 
same name which flows into the White Sea. 



RIVERS. 53 

RIVER BASINS. SQUARE MILES. 

Thames 5,000 

Rhine ...!.. 89,000 

Danube 312,000 

Ganges 443,000 

Volga 653,000 

Blississippi . . ' . . . . 1,100,000 

Amazon 1,920,000 

The velocity of a river depends in a great 
degree on the nature of the country in which it 
takes its rise, and which it traverses. The 
Thames has its source at an elevation of only a 
few hundred feet above the level of the sea, and, 
since its whole course lies through a comparative- 
ly level country, it flows with a moderate velocity 
and presents no instances of torrents, rapids, or 
waterfalls, a circumstance which renders it par- 
ticularly available for the purposes of navigation ; 
and thus though it may appear insignificant 
when compared with some of the mighty streams 
on the earth's sm-face, it possesses advantages 
superior to most rivers, having also an unimpeded 
entrance, and being navigable for large vessels to 
the very banks of the metropolis. 

Rivers which take their rise in elevated moun- 
tain districts usually flow with great velocity in 
the earlier part of their course, rushing down in 
torrents, or leaping down in cascades or cataracts. 
When waterfalls are of an impetuous character, 



54 RIVERS. 

they are generally termed cataracts ; when more 
gentle, they are called cascades. "Waterfalls are 
very numerous among the Alps and other moun- 
tainous regions. When a continued slope occurs 
in the bed of a river, rapids are formed. 

It occasionally happens that, owing to local 
peculiarities at the mouths of rivers, accumula- 
tions of sedimentary matter take place in the 
middle of the stream, dividing it into two or more 
branches. By this deposition of alluvium, deltas 
are formed, many of them, those of the Ganges, 
the Orinoco, the Mississippi and the Rhine, for 
example, being of great extent. The term delta 
is applied to these on account of their triangular 
form, like the letter A of the Greek alphabet. 

Some rivers which fall into the ocean, and 
have estuaries or wide channels at their mouths, 
are subject to a great swell or sudden rise of the 
waters when the tide enters the river. This is 
called the bore. It occurs especially at spring 
tides, when a more than ordinarily large volume 
of water enters the mouth of the river. The bore 
may be observed in the Severn^ and some other 
rivers of Great Britain, and is displayed on a 
grand scale in the rivers Ganges and Amazon, 
In the latter river., for three successive days at 
tlie time of the equinoxes, five waves from 12 to 



RIVERS. 65 

15 feet high follow each other up the river, pre- 
senting a truly singular spectacle. 

Most rivers are subject to an occasional, and, 
in some instances, periodical increase in the 
volume of their waters. In the rivers of Great 
Britain and the United States, these flood sea- 
sonSy or freshets, as they are termed, are by no 
means regular, being partly dependent on the 
melting of the snows, and partly on occasional 
heavy falls of rain. In countries where the 
climate is less variable, these flood seasons in 
the rivers are usually periodical. Thus the flood 
seaschi in the Volga, being dependent on the 
melting of the snows in Northern Russia, takes 
place in June. The rise of the Nile being 
dependent on the periodical rains which fall 
abundantly on the mountains where its source 
is situated, almost invariably begins in the middle 
of June, and the waters continue .to increase 
untn the end of August or beginning of Sep- 
tember, when the river is at its greatest height 
and the whole valley of Egypt is usually inun- 
dated. 

The number of considerable rivers which pour 
their waters into the ocean is estimated at about 
440 in the Old World, and 140 in the New 
World. 

The following table gives the length and situa- 



56 



RIVERS. 



tion, and also the termination of some of the 
principal rivers on the surface of the globe. 



■ United States 



Gulf of Mexico 



KIVEB. LOCALITY. TEKMINATIOS. 

Mississippi and Mis- 
souri . . . 

Nile Nubia and Egypt . . Mediterranean Sea 

Amazon .... Brazil Atlantic Ocean . 

Tang-tse-Kiang . . China Pacific Ocean 

Niger Nii-ritia Gulf of Guinea . 

Mississippi proper . United States . . . Gulf of Mexico . 

Volga Russia Caspian Sea . . 

La Plata Brazil and La Plata . Atlantic Ocean . 

St. Lawrence . . . Canada Gulf of St Lawrence 

Indus Hindostan .... Indian Ocean . 

Danube Germany, &c. . . . Black Sea . . 

Euphrates .... Turkey in Asia . . . Persian Gulf 

Oronoco Yenezuela Atlantic Ocean . 

Ganges Hindostan .... Bay of Bengal . 

Colombia or Oregon . United States . . . Pacific Ocean . 

Dnieper Russia Black Sea . . . 

Gariep or Orange . . South Africa .... Atlantic Ocean . 

Ural Russia Caspian Sea . . 

Ohio ...:.. United States . . . Mississippi . . 

_,, . (Switzerland, Germany ? „ _,^ _, 

Rhine < . -,t ,, ^ / North Sea . . . 

^ & Holland . . i 

Seine France English Channel 

Connecticut .... United States . . . Long Island Sound 

Hudson United States . . . Atlantic Ocean . 

Thames . . . • . England Noi-th Sea . . . 



MILES. 

4200 



3600 
3300 
3000 
2400 
2200 
2200 
2000 
1800 
1700 
1700 
1550 
1500 
1500 
1200 
1050 
950 
950 



440 
400 
350 
215 



Note. — This list of rivers is changed but slightly from the Eng- 
lish edition. While it should be so thoroughly learned, that the 
pupil can give the locality, termination and length of any river 
taken at random from the table, still the teacher should impress 
the fact that the lengths of many of the largest rivers of the globe 
have never been obtained with exactness, and that neither this 
table, nor in fact any table in the present state of geographical 
knowledge, can be appealed to as final authority upon the 



LAKES. 57 

length of rivers. We find, on collating various statistics bearing 
upon this point, a deviation in one instance of 1300 miles from 
the length given by Miss Zornlin. This, it is true, is an extraor- 
dinary case J the river is the Kiang-Ku or Yang-tse-Kiang, 
an immense and splendid stream, but not well known. 



LAKES. 

Lakes are of diiFerent kinds. Some may be 
considered as tanks or reservoirs which receive 
the first outbreakings of a spring ; and in lakes 
of this description, if the volume or quantity of 
water be of small amount, the evaporation from 
the surface may be sufficient to dispose of the 
whole supply from the spring ; and therefore 
such a lake will require no outlet. Such is the 
case with a large number of small lakes and 
ponds in all parts of the globe. K the amount 
of water sent forth by a spring be more than will 
fill the hollow which forms the basin of the lake, 
the water will scoop out for itself a channel, and 
issue forth either in the form of a little brook, of 
a rivulet, or of a river. Many important rivers 
have their sources in small lakes. Thus the 
river Volga commences its course by issuing 
firom the small Lake of Ternoff^ the Amazon from 
Lake Reyes^ and the Mississippi from Lake 
Itasca. 



58 LAKES. 

Other lakes consist of basins or reservoirs 
which occur in the line of a river's course, into 
which its waters flow, and which, having filled 
the cavity, issue forth from some other point. A 
river may form numerous lakes of this kind in 
its progress. Thus the Mississippi^ in the earlier 
part of its course, passes through no less than 
eight such lakes, some of which are of consider- 
able size. Most of the lakes or loughs* of Ireland 
are thus formed. Indeed, the Shannon river is 
but a succession of these. 

Some lakes consist of basins or cavities into 
which rivers flow, but which on account of their 
depression or their mountainous surroundings 
have no outlet. Instances of this clas^ are the 
Caspian Sea and the Sea of Aral, which are 
great inland lakes, and Lake Asphaltites or the 
Dead Sea. The rivers which supply them are 
continually bringing down a portion of salt which 
they have dissolved from the soil through which 
they pass, and which occasions the brackishness 
of most river water. As evaporation proceeds, 
the purer portions only are removed, the saline 
matter remains, and thus salt lakes are formed. 
The Dead Sea receives the waters of the Jordan 
on the north, of the Arnon on the east, and of 

* Pronounced lochs^ nearly. 



LAKES. 59 

the brook Kedron or Cedron on the west. Its 
waters are Salter than those of the ocean, and 
this fact is accounted for, partly by the explana- 
tion just offered, and partly by the circumstance 
that it is constantly dissolving the blocks of salt 
which are found on its southern shore. 

Lakes are sometimes formed in the craters of 
extinct volcanoes, and in such cases the waters 
are usually strongly impregnated with sulphur 
and bitumen. 

Some lakes are periodic; that is, subject to 
have their basins alternately empty and full of 
water. Of this description is the Lake of Zirk- 
nitz, in Carniola, which in midsummer is dry 
and allows a luxuriant crop of grass to cover its 
bottom, but is filled in autumii, and continues full 
through the winter and spring. 

The lakes in the British Isles are of small size, 
Windermere is the largest English lake, not ex- 
ceeding eleven miles in length and one mile 
in width. The largest European lakes are the 
lakes of Ladoga and Onega in Russia. The 
Caspian Sea may be considered as the largest 
lake on the face of the globe, its length being 
about 700 miles, and its width about 210 miles. 
North America contains the largest fresh water 
lakes in the world, and, indeed, a vast chain of 
connected lakes occupies a wide surface of coun- 



60 THE OCEAN. 

try in its more northerly regions. This chain 
includes Lak^es Superior^ Huron, Michigan, Erie, 
and Ontario, the surplus waters of which, after 
having formed the grand Fall of Niagara be- 
tween Lakes Erie and Ontario, are discharged 
into the Atlantic by the river St. Lawrence. 
The frequent and violent storms to which large 
lakes are eminently subject are produced by the 
violent rushing of the wind down the sides of 
the mountains by which they are surrounded. 
The scenery of small lakes is the most beautiful 
in the world. 

THE OCEAN. 

The extent of the vast mass of waters called 
the Ocean greatly exceeds, as we have already 
seen, that of the dry land on the surface of the 
globe. This is an arrangement of great impor- 
tance in the natural world, for abundant supplies 
are thus afforded, by evaporation from its vast sur- 
face, for the large amount of moisture required 
to water the earth, which descends in the form 
of showers and devf. 

The ocean consists of one great fluid mass ; 
and in accordance with the laws by which fluids 
are governed, its waters flow into and occupy the 
great depressions on the Earth's surface which 



THE OCEAN. 61 

form its bed, maintaining a general level in all 
parts of the globe, whatever may be the undula- 
tions of the ground on which it rests. 

Although thus in fact one mighty whole, the 
ocean has received in geographical descriptions 
several nominal divisions and subdivisions. 

The two principal divisions of the ocean are 
those of the Atlantic and the Pacific^ which are 
formed by the two great continents. The Austral 
or Southern Ocean may be regarded as forming 
a third division, and occupies that portion of the 
ocean not included in the two former divisions. 
Its limits may be traced by a line passing round 
the globe, and touching the Cape of Good Hope, 
Cape Horn, and the southern extremity of Tas- 
mania (Van Diemen's Land). 

The Atlantic Ocean is sometimes subdivided 
into three portions ; the Northern Ocean, which 
includes the Polar Seas, and extends to an imag- 
inary line drawn across the ocean, from the 
northern extremity of the British Isles to the 
southern extremity of Greenland; the North 
Atlantic, extending from that line to the Equa- 
tor ; and the South Atlantic from the Equator to 
the southern extremities of Africa and America, 
that is, to the Austral or Southern Ocean. 

The Pacific has also three subdivisions ; the 
North and the South Pacific, and the Indian Ocean: 



62 THE OCEAN. 

The division between the North and the South 
Pacific is marked by the line of the Equator ; 
and the latter extends to the southern coasts of 
Australia. The Indian Ocean comprises the 
seas extending from Australia and the western 
limits of the Indian Archipelago to the eastern 
coasts of Africa. 

In various parts of the great continents, deep 
inlets, called branch or inland seas, occur, pene- 
trating far into the interior, and communicating 
with the main ocean either by narrow straits, as 
the Red Sea, the Mediterranean, and the Baltic ; 
or by wider channels, as the White Sea, the 
Yelloiv Sea, Baffin^ Bay, &c. 

Smaller inlets of the sea are of frequent occur- 
rence, especially in districts where mountain 
ranges approach the borders of the ocean. 
Such are the lochs of Scotland, the voes of the 
Shetland Isles, and the fiords of the coast of 
Norway. The term lagoon is usually applied to 
the lake-like inlets on the shores of the Adriatic 
Sea, in the midst of one of which the city of 
Venice is built. 

The ocean varies greatly in its depth, but is sup- 
posed generally speaking, to be deepest at a dis- 
tance from land, and shallowest in channels and 
straits and near islands, though it differs much 
in its depth in the immediate vicinity of dry land, 



THE OCEAN. 63 

according to the character of the surface, whether 
the shores may be flat or rise abruptly from the 
sea. The mean or average depth of the sea 
round the comparatively level coasts of South 
Britain, is considered not to exceed 120 feet ; off 
those of Scotland, to be about 360 feet ; and off 
the western coast of Ireland, where rocks of a 
precipitous character abut upon the sea, to have 
the depth about 2000 feet. In some parts of the 
mid- Atlantic Ocean the plumb-line has been let 
down to the depth of 27,000 feet, without reach- 
ing the floor of the ocean, and it is probable that 
we shall never be able to ascertain with certainty 
the greatest depth, for no line can be made strong 
enough to bear its own weight, and yet be 
manageable, if we attempt to go much beyond 
five mUes and a half (27,000 feet). 

The temperature of the ocean's surface appears 
generally to agree with that of the climate in 
which it is situated, that is, with the temperature 
of land at the level of the sea. In warm climates 
the temperature of the deep sea diminishes with 
the depth below the surface, until a certain depth 
is reached, below which it appears to retain an 
equable temperature, this being about 40° Fah- 
renheit. In the Polar Seas, where the tempera- 
ture at the surface of the ocean is lower than 
40°, the temperature is found to increase until it 



64 THE OCEAN. 

reaches that point. About N. lat. 70"^ the tem- 
perature of the ocean is considered to be the 
same at all depths. 

The waters of the ocean are salt, holding in 
solution various saline matters which impart to 
to them a disagreeable taste, and render them 
unfit for the beverage of man. The saline in- 
gredients amount to rather more than thirty-five 
grains in a thousand grains of sea-water. The 
most abundant of these is chloride of sodium, or 
common salt, which in general forms above one- 
third of the whole saline matter. Besides this, 
sea-water contains some magnesia, lime, potash, 
and traces of iodine and bromine. The specific 
gravity or weight of sea-water is greater than that 
of pure water. Pure water (at the temperature 
of 60°) is reckoned at 1000 ; the specific gravity 
of sea-water is 1027. Sea-water in the vicinity of 
land is usually less salt than in the deep ocean ; 
probably owing to the drainage of the land and 
the influx of rivers. For the same reason, branch 
or inland seas are ordinarily less salt than the 
ocean. Thus, the waters of the Baltic Sea, 
into which numerous important rivers pour their 
streams, are much less salt than those of the 
ocean. 

The Mediterranean Sea forms an exception to 
the general rule of the inferior saltness of branch 



ICEBERGS. 65 

or inland seas, the waters of that sea being found 
to contain a larger proportion of saline matter 
than those of the Atlantic Ocean. This pecu- 
liarity is supposed to be attributable to the prox- 
imity of this branch of the ocean to the burning 
sands of Africa, and also to the parching winds 
which, passing over this sea after traversing 
those desert tracts, cause an extraordinary 
amount of evaporation to take place from its 
surface. 

The freezing point of water is affected by its 
saline contents. The freezing point of fresh 
water being 32° Fahrenheit, that of sea-water is 
28° or 29°. The waters of the ocean therefore 
require a greater degree of cold than do those 
of a fresh water lake, to convert them into a 
solid mass of ice ; and it is only in very cold 
climates that ice is formed in the open sea. 

Icebergs^ or mountains of ice, though occa- 
sionally formed in the sea itself by the accumu- 
lation of ice and snow, appear more frequently 
to consist of glaciers which have been originally 
formed on the shores, and which, becoming de- 
tached and falling into the water, have been 
floated out to sea. Icebergs are met with in 
great numbers about N. lat. 70^, but they are 
sometimes carried by currents into much lower 
latitudes, having been observed in the northern 
5 



60 THE OCEAN. 

hemisphere in the parallel of 40°, and in the 
southern hemisphere in that of 36°. Some ice- 
bergs are of enormous size, being two or three 
hundred feet in height above the water, and pro- 
bably having about eight times that depth below 
the surface, and extending sometimes for two 
miles or more. These are found not so often 
alone as in groups, and the surface which they 
expose is sometimes so great as perceptibly to 
freshen the sea in their vicinity. 

Sea-water when seen in small quantities seems 
to be colorless, but when seen in a large mass, 
its natural color appears to be sky-blue. Since 
the water acts like a mirror and reflects the hues 
of the changing skies, it may often appear to 
assume different tints, as the sky is clear or 
cloudless, or according to the position of the 
sun. Thus at times it will appear of a dull 
dead color, at others it will present varied tints 
of purple and green, at others, shine like bur- 
nished gold. 

In some cases, however, the general color of 
the ocean is affected by the nature of its bed, 
especially if the water be shallow ; for yellowish 
sand mingling its color with the natural blue 
tint of the ocean imparts a greenish hue to the 
whole mass. If the bed of the sea be red, as is 
the case in some parts of the Mediterranean, 



ITS COLOR. 67 

(probably owing to the red coral which abounds 
in some parts), this red hue combined with the 
bright blue of the waters of that sea gives a pur- 
ple tint. When the water is very clear, the red 
hue prevails, and the waters appear tinged with 
that color. Thus, in the Bfiy of Loango, off the 
western coast of Africa, the water appears so 
red that it might be supposed to be mixed with 
blood. 

Sometimes color is imparted to the ocean by 
the presence of innumerable minute living crea- 
tures. Thus, in the Polar Seas, the water in 
some parts appears of a green hue, in conse- 
quence of its being filled with myriads of yellow 
semi-transparent medusce. From a similar cause, 
the ocean in other parts appears of a brown 
color, in others of a milky white, and in others 
of a deep red hue. 

The luminosity or phosphorescence of the ocean 
appears in some instances to be produced by 
decaying animal and vegetable substances, but 
in others to arise from the presence of vast, num- 
bers of living animals, which, like the glow- 
worm, have the power of emitting light. Some 
of these luminous animals shine like liquid 
silver, and others sparkle like amethysts and 
emeralds. 



68 TIDES, WAVES, AND CURRENTS. 



Vin. TIDES, WAVES, AND CURRENTS. 

The waters of the ocean are in perpetual 
movement from the effects of tides ^ winds ^ and 
currents. 

The waters of the ocean are retained in their 
bed on the surface of the globe by the attraction 
of gravitation^ that is, by the power which has 
been imparted to all particles of matter to draw 
towards them or attract other .particles of matter. 
This power of attraction is great in proportion 
to the mass of any body, a large mass of matter 
having a much greater power of attraction than 
a small one ; and as the earth is of much greater 
mass than the particles of water on its surface, it 
attracts them and keeps them in their assigned 
place. But the sun and moon also possess this 
power of attraction, and notwithstanding their 
distance from the waters on the earth's surface, 
attract and draw them up to a certain elevation 
in the wide open ocean. 

The vast mass of the waters being drawn up 
by the influence of the moon into a great moun- 
tain or curve of water in the wide open sea, 
forms what is termed the great primary wave, 
or tidal wave. When the waters of the ocean 



TIDES. 69 

are thus drawn up to form this great wave, they 
necessarily recede from our shores, thus giving 
rise to ehb tide or loiv water. But when the tem- 
porary attraction ceases, the waters having been 
raised above their ordinary level naturally flow 
down and spread in all directions, returning to 
our shores, and ioxmin^ flood tide or high water* 
This culmination or rising of the waters in 
this great wave takes place twice in twenty-four 
hours and fifty minutes. The combined influ- 
ence of the sun and moon at new and full moon 
augments the size of this wave, and causes the 
spring tides at those periods. The great Atlan- 
tic tidal wave arrives first at the western shores 
of the British Isles ; it then divides into two 
branches, the principal of which passes round 
the coast of Scotland, and travels southward 



* An attempt to popularize the theory of tides must lead to 
much misconception, but Miss Zornlin's explanation is so lucid, 
so far as it extends, that we have preferred to retain it, with the 
hope that it may induce the pupil to consult more elaborate works, 
and make himself master of this interesting subject. It will be 
noticed that no explanation is attempted of the flood-tide on the 
side of the earth which is turned from the moon. If the class is 
sufficiently mature to profit by the explanation, the teacher can 
avail himself of the black-board to illustrate that portion of the 
subject. For a full and lucid exposition of the theory of the 
tides, the editor would refer to Murray's Encyclopaedia of 
Geography. 



:70 TIDES, WAVES, AND CURRENTS. 

until it reachjes the mouth of the Thames, where 
it encounters the lesser branch, which has swept 
along the western shores. High water at the 
various points along the coasts is dependent on 
the arrival of this great wave, though some va- 
riations are caused by local peculiarities, such as 
the form of the coast, &c. 

The height of the tides varies greatly in the 
different parts of the earth, but as a general rule 
it depends upon the nature of the shore. Where 
the waters accumulate, as in those bays which 
communicate with the sea by wide channels, 
the tides rise very high ; as for example, at 
Bristol in England, where the rise is about fifty 
feet. Perhaps the most remarkable instance is 
the well-known tide wave of the Bay of Fundy, 
w^hich in some seasons of the year attains the 
height of seventy feet. At the sh6res of small 
islands, on the contrary, the elevation of the 
wave is not great. At St. Helena it never ex- 
ceeds three feet, and at some of the islands of 
the Pacific the spring tide is but five feet in 
height, the neap tide not over two-and-a-half. 

The waves of the sea which are caused by 
the action of the wind, and which are called 
secondary waves, or wind waves, are of a totally 
different character from the tidal wave. There 
is much appearance of confusion in an agitated 



WAVES AND CURRENTS. 71 

sea, but in the midst of this apparent disorder 
order reigns, and it seems to be in a great meas- 
ure owing to the continual slight shifting of the 
wind, that waves appear so frequently to cross 
and intercept each other. The influence of the 
wind is supposed not to extend to a greater 
depth than forty or fifty feet, the deep sea, 
though raised in a great mass by the grand 
tidal movement, being free from agitation. 
Wind waves at a distance from the shore are 
comparatively long and low, but as they ap- 
proach the coast where the water is shallow, 
they assume a greater curvature, and fall on 
the beach either in gentle ripples, or in mag- 
nificent breakers, according to the depth of the 
water and the force of the wind. 

The heavy swell which occasionally takes 
place on the northern coasts of some of the 
West Indian Islands, called the ground sea, is 
supposed to originate in distant storms of wind 
in the Atlantic Ocean. The sea, although the 
air is calm, suddenly rises as if agitated by a 
heavy gale, and wave follows wave in quick 
succession, crested with foam and bursting on 
the beach with great impetuosity. 

Currents* in the ocean arise from various 

* The ehart of the currents will be found on page 18. 



72 TIDES, WAVES, AND CURRENTS. 

causes: they may be produced by long-con- 
tinued gales of wind ; by the melting of. the 
polar ice ; or by any cause that may give rise 
to onward movements of limited portions of 
the great mass of waters. Some currents of 
the ocean are permanent : the most remark- 
able of these are the polar currents^ and the 
equatorial currents. 

The polar currents are produced by the per- 
petual movement of the waters from the polar 
regions to the equator. In accordance with 
the laws of mechanics, an accumulation of 
the waters of the ocean takes place in that 
part of the globe which has the greatest veloc- 
ity of motion : and as the earth in turning 
on its axis moves with far greater velocity at 
the equator than it does in high latitudes, the 
waters consequently flow continually towards 
that line, thus forming currents in the ocean 
which move from the north and south poles to 
the equator. 

This culmination or accumulation of the 
waters of the ocean at the equator, tends to 
produce the equatorial currents, which consist 
of the continuous progression of the tropical 
seas in a westerly direction. When the mass 
of water brought by the polar currents arrives 
at the equator — coming as it does from regions 



CURRENTS. 73 

where it naturally has less velocity — it does 
not at once acquire thd velocity of the earth at 
the equator ; and since the rotation of the earth 
is from west to east, this portion of the water 
lagging behind, forms a stream or current which 
has an apparent motion from east to west, that 
is to say, apparent as regards the earth, but 
real in relation to the adjacent land and water. 
The trade winds, which in this zone bl6w per- 
petually in the same direction, lend their aid in 
maintaining the equatorial current. 

An extensive system of currents appears to 
commence in the Antarctic Ocean. A current 
of cold water flowing northwards joins the equa- 
torial current in the Pacific. Entering the In- 
dian Ocean, it maintains its westerly course 
until it approaches the shores of Africa. Then 
bending southwards, it rushes through the Mo- 
zambique Channel, and doubling the Cape of 
Good Hope, travels northwards until it arrives 
at the Bight of Benin. This current there joins 
the equatorial current, and crossing the Atlantic 
from the coast of Guinea to that of Brazil, it is 
divided into two branches by the projecting 
headland at Cape St. Roque. The smaller 
branch flows southwards along the eastern coast 
of South America, where it meets the Antarctic 
current to which it owed its commencement. 



74 TIDES, WAVES, AND CURRENTS. 

The northerly branch of this current skirts the 
shores of Brazil and Gniana, where it receives 
the waters of the rivers Amazon and Oronoco. 
After passing the island of Trinidad, this great 
oceanic current enters the Gulf of Mexico. The 
waters there acquire the high temperature of 
about 88° Fahrenheit. Sweeping round that 
extensive inland sea, they again pour forth into 
the Atlantic, forming the most powerful of 
known currents, called the Gulf Stream. On 
issuing from the Gulf of Mexico this current 
of warm water rushes with considerable force 
through the straits of Bahama. Then taking 
a northward course, it travels along the eastern 
shores of North America, until it approaches 
Newfoundland, where it is turned to the east- 
ward, by an opposing cold current which sets in 
from Baffin's Bay. It now maintains an easter- 
ly direction, and crossing the Atlantic arrives 
at the Azores in about twenty-eight days, and 
divides its waters on the coast of France and 
Spain ; a portion goes southward, and at length 
joins the grand current which sets from the 
coast of Guinea, while a portion travels north- 
wards. Thence it extends to the Bay of Biscay, 
and travelling northwards skirts the western 
coasts of Europe, sometimes wafting to and 
depositing on its shores and also on the western 



THE ATMOSPHERE. 



n 



coasts of the British isles the products of tropi- 
cal America, and probably imparting to the 
whole of the Northern Ocean some portion of 
its more elevated temperature. 



IX. THE ATMOSPHERE. 

The Earth is surrounded by its atmosphere^ 
which like a transparent covering envelopes it 
and revolves with it. This atmosphere is con- 
sidered to extend to the height of about forty or 
fifty miles, its height being greater at the equa- 
tor than at the poles. 

The mV, which expands into and forms this 
atmosphere, is an elastic fluid consisting of a 
mixture (not a compound) of oxygen gas and 
nitrogen or azotic gas, in the regular proportions 
of twenty-one parts of oxygen to seventy-nine 
parts of nitrogen. The atmosphere also con- 
tains a small quantity of carbonic acid gas, and 
a yet smaller quantity of ammonia. Water in 
the form of vapor, in which state it is invisible, 
is also always present in the atmosphere, though 
the quantity is subject to great variations. All 



76 THE ATMOSPHERE. 

these substances move freely among each other, 
and are continually changing places ; the oxygen 
being ever ready to perform the office assigned 
to it of sustaining life and combustion ; the car- 
bonic acid, to promote the growth of vegetation ; 
the nitrogen, to perfect the fruits of the earth; 
and the vapor, to descend to the thirsty ground 
in the form of showers and dew. 

The air being elastic is therefore capable of 
expansion^ or of spreading in all directions ; and 
also of being compressed into a smaller space ; 
and when compressed, becomes more dense^ or 
thicker, and consequently is heavier. And thus, 
if a closed vessel of any size be filled with com- 
pressed air, and another of similar size be filled 
with air which has not been compressed, the 
former is found to have more weight than the 
latter, in proportion to the degree of compres- 
sion. 

The consequence of this weight or elasticity 
of the air is, that it is much lighter and thinner 
in the upper regions of the atmosphere than 
nearer the earth's surface : for at the level of the 
sea, the air has the weight of the whole atmos- 
phere above it to compress it and give it greater 
density ; but at an elevation of 10,000 feet, the 
pressure from above being diminished, the air is 
less dense and lighter: because its elasticity 



ITS WEIGHT. 77 

causes it readily to become compressed near the 
level of the sea, and to expand in the upper re- 
gions of the atmosphere. And hence, air is 
thinner or more rarefied on elevated mountains 
than at the level of the sea ; the decrease in 
density being in regular proportion, according 
to the height above the sea level. In conse- 
quence of the air becoming so much thinner or 
more rare at great elevations, travellers who 
ascend lofty mountains usually find their res- 
piration much affected, and they are sometimes 
compelled to seek relief by throwing themselves 
on the ground, which enables them to breathe 
more freely. 

The w^eight of the atmosphere at the level of 
the sea is equal to about fourteen pounds and a 
half on every square inch. This is called the 
weight of an atmosphere^ and is balanced by a 
column of mercury thirty inches in height ; but 
at the elevation of 18,000 feet, it would be bal- 
anced by a column only fifteen inches in height, 
at that of 36,000 by one only seven inches and 
a half in height, and so on. It is on this prin- 
ciple that the mercurial barometer has been 
constructed ; and since the mercury in the ba- 
rometer is found (with slight local variations) 
to stand at the same point at all places at the 
level of the sea, and to fall in a regular ratio as 



78 THE ATMOSPHERE. 

we ascend above that level, this instrument 
forms a most useful standard for measuring the 
altitude of any place, either mountain, hill, or 
plain, to which a barometer can be carried. 
The mercury is considered to fall one degree 
in about every 950 feet. Baron de Humboldt, 
when he visited Chimborazo in the Andes, 
found that at the level of the sea near that 
mountain the barometer stood at 20° ; but at 
the height to which he ascended, it fell to four- 
teen inches, eight lines ; and accordingly he 
came to the conclusion that the elevation he 
had attained was 19,353 feet. Air is subject 
to variations in its density, even at the same 
level, being affected by the presence of vapor 
in the atmosphere, by currents of wind, by elec- 
trical action, &c.; and hence the mercury usually 
falls at the approach of rain, of wind, or of a 
thunder-storm, and hence the daily and even 
hourly fluctuations which take place in the 
barometer. 

The temperature of the air likewise diminishes 
as we ascend above the level of the sea. The 
rate of decrease does not appear to be absolutely 
regular, but is considered to be about one degree 
of Fahrenheit's thermometer for about every 340 
feet; and accordingly (though variations occur 
from local causes) the thermometer generally 



WINDS. 79 

stands lower in elevated districts, than in those 
nearer the sea level in the same latitude ; and 
hence it is, that even in the hottest regions of 
the earth, very lofty mountains are covered with 
perpetual ice and snow. 



WINDS. 

The aerial currents called winds appear to be 
caused by partial changes in the density of the 
atmosphere, in great measure arising from the 
different distribution of heat in various parts of 
the earth's surface. When air is warmed by 
the heat of the sun or any other cause, it be- 
comes less dense, and the space it occupies has 
therefore more capacity^ or more room to admit 
an additional portion of air. If an adjacent 
stratum of air be cooler, it will, on coming in 
contact with the warmer air, expand and pour 
into the space occupied by the latter, thus form- 
ing a current, or wind. The greater the differ- 
ence between the temperature of the one por- 
tion of air and the other, the greater will be the 
force with which the cold portion will rush into 
the space occupied by the warm portion, or, in 
other terms, the more violent will be the wind. 
This is well displayed in the violent winds 



80 THE ATMOSPHERE. 

which in some warm regions almost daily rush 
down from the adjacent mountains into the 
plains, as soon as the latter become heated by 
the mid-day sun. 

In the United States, and, generally speaking, 
in temperate climates, the winds are vai'iahle ; 
but in some parts of the globe they blow with 
great regularity, and in others are subject to 
periodical changes. 

The most remarkable permanent winds are 
those termed the trade-winds. The air at the 
surface of- the sea between the tropics is much 
warmer than in high northern and southern lati- 
tudes ; and since air expands and becomes less 
dense when heated, the light warm air in inter- 
tropical regions perpetually rises from the sur- 
face, and its place is as perpetually supplied by 
the colder air, which glides in from the regions 
both to the north and to the south of the tropics. 
If it were not for the earth's rotation on its axis, 
these would be merely northerly and southerly- 
winds; but, like the equatorial currents in the 
ocean, these cool currents of air, coming from 
regions which have not an equal velocity of 
rotation with the air at the equator, pause and 
hang back, and thus these aerial currents ac- 
quire a westerly direction, forming permanent 
north-easterly winds in the northern hemisphere, 



WINDS. 81 

and south-easterly in the southern. In the im- 
mediate vicinity of the equator, where the two 
aerial currents from the north and south meet, 
they so completely counteract each other, that a 
zone about five degrees and a half in width ex- 
ists, which is comparatively calm and free from 
any prevalence of easterly winds, though subject 
to storms of thunder and lightning. This zone 
is called the variables. The trade-winds form 
two great belts, extending on either side of this 
zone, to north and south latitude 28°. A devia- 
tion from their regularity is caused by the prox- 
imity of land ; and they are less regular in the 
Pacific* than in the Atlantic, and less steady in 
the North than in the South Atlantic. 

While this interchange of air gives rise to east- 
erly winds in the tropical seas, it at the same 
time causes ivesterly winds to prevail in higher 
latitudes. The warm air which has changed 
places with the cooler northern and southern 
air, cari'ies with it the velocity belonging to its 
former situation near the equator, into regions 
where the earth's surface moves at a slower pace, 

* The innumerable islands of this ocean will account for thig 
"want of regularity, while the fact that the westward current 
traverses the South Atlantic may not be without weight in de- 
termining the reason of the greater uniformity of the trade-wind 
in that ocean. 

6 



82 THE ATMOSPHERE. 

and consequently, as this air travels northwards 
or southwards, it moves at a more rapid pace 
than that portion of the earth's surface it now 
occupies, thus giving rise to the south-westerly 
gales so prevalent in our latitude, and to the 
north-westerly gales of the same portion of the 
southern hemisphere. 

The monsoonsy or periodical winds of the In- 
dian Ocean, appear to owe their origin to the 
same cause which gives rise to the trade-winds, 
though they acquire a different character in con- 
sequence of the proximity of land. In the south- 
ern portion of the Indian Ocean, which is remote 
from this cause of disturbance, the trade-wind 
blows with its wonted regularity ; but in the seas 
occupying the region between the eastern coast 
of Africa on the one side, and the Malayan pe- 
ninsula and Sumatra on the other, the course of 
the trade-wind is reversed for half the year. This 
change occurs from April to October : the sun at 
that period being vertical north of the equator, 
and the land in the adjacent regions acquiring in 
consequence a high temperature, and the air over 
the sea being cooler than that over the land, a 
south-west wind prevails. This wind, called the 
south-west monsoon, commences at about three 
degrees south of the equator, and, passing over 
the ocean, arrives charged with moisture, and 



WINDS. 



83 



accordingly usually deposits copious supplies of 
rain in India and some of the adjoining territo- 
ries. In the remaining half of the year, that is, 
from October to April, the wind resumes the 
ordinary north-easterly direction of the trade- 
wind. 

Sea breezes occur in regions bordering on the 
sea in hot climates. They are produced by 
causes similar to those which give rise to the 
south-west monsoon. The surface of the land 
being more heated dm'ing the day than that of the 
sea, and the air consequently becoming rarefied, 
the cooler heavier air rushes in from the surface 
of the sea, thus giving rise to the sea breeze. 
This usually commences at about ten o'clock in 
the morning, and continues throughout the day 
until about six o'clock in the afternoon, when it 
gradually sinks away. In some situations the 
reverse takes place at night, the sea at that time 
retaining a higher temperature than the adjacent 
land and causing a land breeze to spring up. 
This usually commences at about eight o'clock 
in the evening, and dies away before six in the 
morning ; it is much fainter and less regular than 
the sea breeze, and also of less common occur- 
rence ; for the sea breeze may generally be ob- 
served in aU warm countries, and even, in sunny 
weather, on our own shores. 



84 THE ATMOSPHERE. 

Hurricanes are storms of wind which sweep or 
whirl round in a regular course, and are at the 
same time carried onward along the surface of 
the globe. In the northern hemisphere the whirl- 
ing motion follows the course of east, north, 
west, south, to east again ; in the southern hemi- 
sphere it takes the opposite course. In the At- 
lantic Ocean, the principal region of hurricanes 
lies to the eastward of the West Indian Islands. 
They are of frequent occurrence in the Indian 
Ocean, at no great distance from the Island of 
Madagascar. The typhons of the China Seas 
and the ox-eye of the Cape of Good Hope are 
also considered to be revolving storms. 

The tornadoes of the western coast of Africa, 
the pamperas of South America, and the storms 
called arched squalls^ appear to be of a different 
character, and not to possess a revolving motion. 

The sirocco of Italy and Sicily, and the solano 
of Spain, as also the simun or simoon (sometimes 
called simoom) of Arabia, and the harmattan of 
Western Africa, are all winds which owe their 
origin to the parched and heated surfaces of 
Africa and Arabia. The principal difference 
between these winds appears to be, that the 
sirocco and the solano acquire some moisture in 
their passage across the Mediterranean Sea, and 
therefore do not possess that extreme degree of 



VAPOR. 



85 



aridity which forms the distinguishing character 
of the simun and the harmattan. * 

Water in the form of vapor is always present 
in the atmosphere. Warm air is capable of hold- 
ing suspended a larger quantity of moisture than 
cold air, and therefore the amount of vapor present 
in the atmosphere is subject to great variations. 
If water be exposed to the air, it gradually disap- 
pears, finding its way into the atmosphere by the 
process called evaporation. If not exposed to the 
air, as for instance, if kept in a closely-corked bot- 
tle, the quantity will remain undiminished for 
years ; but if we leave the bottle uncorked, the 
water will ere long be dried up, or evaporated ; and 
if we pour the water into a plate, a larger sur- 
face being thus exposed to the air, the process of 
evaporation will be carried on much more rap- 
idly. Warm air being capable of holding a 
larger quantity of moisture than cold air, evapo- 
ration proceeds more rapidly in warm than in 
cold weather, and hence a pond, or moist garden 
mould, will be dried up much more rapidly in 
summer than in winter. 

* The subject of Winds is becoming better understood and 
more reducible to law, every year. It would be a triumph of 
physical science, too great to expect, to be able to determine the 
exact sequence of winds in any portion of the earth, and thus to 
predict the state of the weather with certainty, yet we may be 
assured that our knowledge of winds is but in its infancy, and 
that large discoveries are yet to be made in this direction. 



86 THE ATMOSPHERE. 

The fact that warm air is capable of holding 
a larger quantity of moisture than cold air, ac- 
counts for the formation of dew, A cubic foot of 
air, at the temperature of 32'' (the freezing point), 
has not capacity for holding more than two 
grains and a half of moisture, while at the tem- 
perature of' 70°, it will hold about five grains and 
three-quarters; and in intermediate proportions 
between these temperatures. It will therefore 
be evident that if the air become heated during 
the day, its capacity for holding vapor being thus 
increased, evaporation will proceed with greater 
or less rapidity, and the air will become more or 
less charged with moisture, according to the 
nature of the surface on which it rests or over 
which it passes, and its own temperature. But 
when a cold night succeeds to a hot day, the air 
being no longer capable of holding this watery 
vapor, it mil, as the temperature gradually di- 
minishes, be gradually and gently deposited in 
the form of dew. Dews will therefore usually be 
most abundant when cool nights succeed warm 
days, which in our climate more frequently hap- 
pens in summer and autumn than in spring 
and winter. The air usually becomes much 
colder on clear nights than when the skies are 
obscured by clouds, and accordingly dew is gen- 
erally more abundantly deposited on starlight 
than on cloudy nights. 



DEWS. 87 

It is also essential for the copious formation of 
dew that the ground, or other substance on 
which it is deposited, should be much cooler 
than the superincumbent air; for if the ground 
be warm, it will impart its temperature to the 
air near its surface, and dew wUl not be formed. 
The surface of trees, and of vegetation in gen- 
eral, is much colder than that of bare^ rocks, or 
even garden mould, and, consequently, dew^ is 
more abundantly deposited on the herbs of the 
field and the trees of the forest, than on barren 
and stony ground.* 

When the surface of the ground or water is 
warmer than the superincumbent air, mists and 
fogs are frequently formed. And since water and 
marshy surfaces cool less rapidly than dry land, 
mists and fogs are of more common occurrence 
in low damp situations than in dry elevated dis- 
tricts. They are formed by the condensation of 
the vapor^ or, in other terms, its transformation 
into minute drops of water, which, instead of de- 
scending to the earth in the form of dew, remain 
suspended above the land or the water. A re- 

* The pupil must bear in mind that those things which are the 
slowest heated, are also those which best retain their heat ; 
hence rocks, gravel paths, &c. do not readily receive the dew, 
as they radiate slowly the little heat which they have absorbed 
during the day. ^ 



88 



THE ATMOSPHERE. 



markable stationary fog exists off the coast of 
Newfoundland, which owes its origin to the 
chilly atmosphere of that region, and the com- 
parative warmth of the adjacent ocean, the tem- 
perature of which is apparently raised by the 
waters of the Gulf Stream. 

Clouds are formed by the condensation of va- 
por at cofisiderable but various elevations in the 
atmosphere. Vapor is always invisible ; clouds, 
therefore, are not vapor, but water, and consist 'of 
a fine watery powder, the size of each particle 
being exceedingly minute ; and consequently 
they are so light, that clouds formed of an accu- 
mulation of such particles are readily borne 
forward by the wind. Clouds are sometimes 
suddenly formed, and as suddenly disappear ; 
probably owing to sudden and partial changes of 
temperature in the region of the atmosphere 
where they occur. When a considerable differ- 
ence of temperature prevails in the aerial cun-ents, 
or strata of air, which may come in contact in 
the atmosphere, a further condensation takes 
place, and the particles of this fine watery pow- 
der unite into drops, and becoming heavier, fall 
to the earth in the form of rain^ hail, or snow. 
When two strata or currents of air of different 
temperature, moving with great rapidity in op- 
posite directions, come in contact, a sudden and 



CLOUDS. 



89 



heavy fall of rain takes place. K one of these 
strata be very cold, hail may be formed. Snow 
is formed under the same circumstances as rain, 
only the formation takes place in cold climates, 
or at great elevations in the atmosphere. 

Clouds are continually varying in their form 
and appearance, but may be classed under four 
principal heads : — 1, the cirrus ; 2, the cumulus ; 
3, the stratus ; 4, the nimbus. 

' 1. The cirrus is a light fleecy cloud, resembling 
a lock of hair or a feather. 

2. The cumulus^ or summer cloud, is generally 
a massive cloud, of a rounded form ; sometimes 
of small size, and sometimes nearly covering th6 
whole sky ; and occasionally appearing in the 
horizon like mountains capped with snow. 

3. The stratus is a horizontal misty cloud, 
sometimes observed on fine summer evenings 
comparatively near the ground, and often cross- 
ing the middle regions of mountainous or hilly 
districts. 

4. The nimbus^ or rain-cloudy has a uniform 
gray tint ; it is fringed at the edges, when these 
are displayed, but usually covers the whole sky. 

The region of clouds is a zone extending in 
the atmosphere from about one to four miles 
above the surface of the globe. The most ele- 
vated clouds are the light fleecy clouds which 



90 



THE ATMOSPHERE. 



are comprehended under the name of cirrus, and 
the lowest are those which are called stratus. 

The cirro-cumulus.) cirro-stratus .^ and cumulo- 
stratus are only modifications and combinations 
of the above four classes of clouds. 

The quantity of rain that falls in different parts 
of the earth is very variable ; though (since the 
amount of evaporation is augmented by the 
higher temperature of the atmosphere) it may be 
considered as a general rule, that larger quantities 
of rain fall in low than in high latitudes ; and it 
appears that a gradual decrease in quantity takes 
place, as we recede from the equator towards the 
lipoles. In the island of Tahiti, the annual fall of 
rain amounts to 150 inches ; at Bombay, to 80 
inches ; in the British Isles, to about 25 inches ; 
at St. Petersburg, to only 17 inches. 

Rain is more abundant in the New than in the 
Old World, which is probably owing to the dif- 
ferent configuration of the two great continents, 
the longer and narrower being more exposed to 
the moist winds from the sea than the shorter 
and broader. Thus the annual fall of rain in 
tropical America amounts to 115 inches, whilst 
in similar parallels of latitude in the Old World 
it does not exceed 76 inches. In the temperate 
zone in the New World, again, the annual quan- 
tity of rain is 37 inches, whilst in the Old World 
it is only 31^ inches. 



RAIN. 



91 



In some parts of the earth, extensive tracts ex- 
ist, where rain is never known to fall, or if at all, 
only at intervals, and then in small quantities. 
The rainless districts in the New World include 
the flat territories of Northern Chili and Peru, 
some parts of Mexico, and some parts of Cali- 
fornia. In the Old World, an extensive rainless 
band extends from the western shores of Africa 
to the central regions of Asia, including the 
Great African Desert, Egypt, part of Arabia, and 
the Desert of Cobi. Countries so circumstanced 
— unless, like Egypt, rendered fertile by the 
overflowings of a great river — constitute the 
most arid and desolate regions of the earth. 

The quantity of rain which falls in any region 
depends greatly on local causes, such as the va- 
riations of the surface, the prevailing winds, the 
proximity of the ocean, &c. Rain is usually 
more copiously deposited in mountainous and 
well-wooded islands than in any other descrip- 
tion of surface, of which the island of Tahiti 
affords a striking example ; for this beautiful 
island, surrounded as it is by the waters of the 
ocean, covered with luxuriant vegetation, and 
containing mountains rising to the height of 
10,000 feet above the level of the sea, possesses 
every requisite condition for the copious deposi- 
tion of rain. The warmth of the air causes a 



RAIN. 931 

large amount of evaporation to take place from 
the ocean which surrounds it on all sides, and 
this vapor becomes condensed by the cool sur- 
face presented by its elevated and richly wooded 
mountains and' hills ;* and hence the extraordi- 
nary quantity of rain in that island. The rain- 
less disti'ict of Peru, on the other hand, though it 
borders on the Pacific Ocean, is flat and nearly 
destitute of trees, whilst on the inland side the 
Andes rise abruptly to a great elevation, the 
consequence of which is, that the moisture 
brought by the westerly winds from the ocean 
does not become condensed in its passage across 
the hot surface of the flat districts of Peru, and 
therefore rain scarcely, if ever, falls in that region, 
but an abundant deposition takes place on the 
elevated mountains in the interior. And thus 
again, if elevated hills border on the ocean in 
any district, whilst the interior consists of flat 
plains, the moisture usually is deposited on the 
elevated land, and the interior tracts receive 
small supplies of rain ; such is the case with the 
rainless portion of Arabia. 

The annual faU of rain in the British Isles, 
amounts, as has been stated, to about 25 inches ; 
but the quantity differs greatly in the eastern and 

* The pupil will see at once the analogy between the formation 
of rain and of dew in this respect. 



94 THE ATMOSPHERE. 

western districts. The winds sweeping over the 
expanse of the Atlantic Ocean arrive charged 
with abundance of moisture, but deposit a con- 
siderable portion before they reach the inland and 
eastern districts. Thus, the amount of rain that 
falls annually at Glasgow is nearly eight inches 
more than at Edinburgh. The number of rainy 
days in England is estimated at about 154 in 
the year, and on the western coast of Ireland at 
no less than 208. The amount of rain does not, 
however, necessarily depend on the number of 
rainy days, for though the amount of rain within 
the tropics is so much greater, the number of 
rainy days does not usually exceed 78 or 80. 

In: New England the amount of rain which 
falls is greater than in the British Isles, being 
about 38 inches. The quantity decreases as we 
go westward, and at St. Louis it is 32 inches. 
The southern and western states are, however, 
largely affected by the warm and ' moist winds 
j&:om the Gulf of Mexico. 

In intertropical regions the rains follow the 
sun ; that is, when he is north of the equator, 
the rains prevail in the northern tropic, and when 
he is south of that line, in the southern ; this 
forms the rainy and dry seasons, to which coun- 
tries so situated are subject. This does not, 
however, apply to the whole of the intertropical 



CLIMATE. 



m 



regions, for in a zone extending from the fifth to 
the tenth degree of latitude on each side of the 
equator, there are two rainy and two dry seasons. 
In the narrow belt, called the variables j which is 
situated between the regions of the north and 
south trade-winds, rain is almost incessant, ac- 
companied by thunder and lightning. In inter- 
tropical countries, during the rainy season, the 
rain pours down in such torrents, that a larger 
quantity sometimes falls in a few hours than in a 
whole month in the British Isles. 

Beyond the tropics some countries possess 
rainy and dry seasons, and, generally speaking, 
greater abundance of rain falls at particular pe- 
riods of the year, though to the north of the 45th 
parallel of latitude the rains are usually variable, 
of which we meet with an example in the British 
Isles.* 



X. CLIMATE. 



The term climate is used to express the com- 
bination of temperature and moisture which pre- 

* For more enlarged generalizations and more extensive de- 
tails on the subject of rains, the reader will consult that very 
valuable book, Guyot's Earth and Man. 



96 CLIMATE. 

vails at any particular place, or, in more familiar 
terms, the prevailing weather. 

The most prominent causes of diversity of 
climate are, the heat of the sun, the relative posi- 
tion of land and water, and the elevation of land 
above the level of the sea. To these may be 
added, as producing considerable though less 
marked effects, the nature of the soil, the prevail- 
ing winds, the position of mountain ranges, and 
the currents of the ocean. 

The sun is the grand agent in diffusing heat 
over the surface of the globe, the temperature of 
any part being almost wholly dependent on its 
exposure to his rays. Whilst the sun is above 
the horizon of any place, that place is receiving 
heat ; and when the sun is below the horizon, it 
is parting with heat by the process called radia- 
tion, that is, the emission of heat through the 
atmosphere into the regions of space. When- 
ever, therefore, the sun remains more than twelve 
hours out of the twenty-foiu: above the horizon 
of any place and consequently less than twelve 
hours below, the general temperature of that 
place will be above average ; and when the re- 
verse occurs, it will be below average. 

In consequence of the daily rotation of the 
earth, successive portions of its surface are pre- 
sented to the sun's rays ; and owing to the incli- 



CLIMATE. 97 

nation, or slanting position of the earth in its 
orbit, the northern and southern hemispheres are 
brought alternately more directly under the solar 
influence, * and thus by this admirable and bene- 
ficial arrangement the high temperature of the 
tropical zone is moderated, and heat more gen- 
erally diffused over the earth's surface. The 
power of the sun's rays is great, in proportion to 
the vertical or upright direction in which they 
strike the earth ; f and if the sun's rays had been 
permanently vertical in equatorial regions, the 
heat in those parts of the earth would have been 
greatly more intense, and, on the other hand, the 
yet more slanting rays of the sun in higher 
latitudes would not have possessed sufficient 
power to ripen the fruits of the earth in the pres- 
ent temperate zones, nor should we have enjoyed 
the grateful change of spring, summer, autumn, 
and winter. 

We have seen that the earth has been artifi- 
cially divided into five zones ; the torrid, the two 
temperate, and the two frigid zones. If the 
temperature of any place depended solely on 
the heat of the sun, this might convey a tolera- 
bly accurate view of the respective climates in 

*See plate on page 8. 

t It is a singular fact that the earth is three millions of miles 
Dearer the sun in winter than in summer. 
7 



98 



CLIMATE. 



those divisions of the globe ; but it is so greatly 
modified by other circumstances, that considera- 
ble differences prevail in countries situated in the 
same parallels of latitude. 

The relative position of land and water forms 
one leading cause of the diversity of climate. 
The waters of the ocean are of very equal tem- 
perature, widely differing in this respect from the 
surface of the dry land. This arises from the 
waters of the ocean always preserving a nearly 
uniform level, from their tardiness to become 
heated (because water is a bad conductor of 
heat), and from their not possessing the same 
radiating power as dry land, so that they are not 
subject to be cooled down during the absence of 
the sun. The ocean, therefore, has a tendency to 
moderate both heat and cold wherever its influ- 
ence extends. Thus, when a cold wind passes 
over the sea, it becomes warmed, and the rigor 
of winter will be moderated. A hot wind, on 
the contrary, becomes cooled in passing over the 
sea, and the summer temperature of the adjacent 
regions will be lowered. And thus we find that 
the climate of islands and countries bordering 
on the sea usually differs considerably from that 
of the interior of continents, the former generally 
experiencing milder winters and more temperate 
summers than the latter. Such countries are 



CLIMATE. 99 

said to possess an insular climate. Thus, the . 
British Isles possess an insular climate. But 
when any region experiences great severity of 
cold in winter, and at the same time a consider- 
able degree of heat in summer, it is said to pos- 
sess an excessive climate. The most striking in- 
stances of an excessive climate are drawn from 
places like Yakutsk, situated in the depths of 
Siberia, where the difference between the aver- 
age temperature of winter and of summer 
amounts to the astonishing sum of 101.° 

The effect produced on climate by the relative 
position of land and water is exhibited on a 
large scale in the temperate zones of the northern 
and southern hemispheres. The space occupied 
by the waters of the ocean in the southern hemi- 
sphere, is far greater than in the northern, and 
consequently a much more even temperature 
prevails in the regions occupying that portion 
of the globe, than in those in the northern hemi- 
sphere. 

The elevation of land above the level of the sea 
forms another leading cause of the diversity of 
climate. A gradual decrease in temperature takes 
place as we ascend above the level of the sea, 
until we attain a point where perpetual congela- 
lion takes place. This line, which is called the 
snow-line^ or line of perpetual snow, varies in dif- 



100 CLIMATE. 

ferent latitudes, and sometimes, owing to the 
different causes which may give rise to diversity 
of climate, the height of the snow-line differs at 
places in similar latitudes. As a general rule, 
however, it may be considered, that a gradual 
decrease in the elevation of the snow-line above 
the level of the sea takes place as we recede 
from the equator towards the poles. The height 
of the snow-line within the tropics varies from 
16,000 to 17,000 feet above the level of the sea ; 
and (in the northern hemisphere) this line de- 
scends to the very level of the sea at about lati- 
tude 80^ 

The annexed tabular view of the snow-line in 
different latitudes may convey a general idea of 
the limits of perpetual congelation in the north- 
ern hemisphere. 

It will be perceived that the snow-line is higher 
at the distance of twenty degrees from the equa- 
tor, than at the equator itself. This is explained 
by the circumstance, that the sun at the equator 
is never more than twelve hours above the hori- 
zon ; whereas, near the tropics, the longest days 
are thirteen hours and a half in length ; and as 
the sun at that period of the year is vertical, or 
nearly so, in that portion of the globe, the summer 
heat, on which the line of perpetual snow de- 
pends, is greater than immediately under the 
equator. 



LATITUDE. 
30 40 50 




TABULAR VIEW OF THE SNOW-LINE IN DIFFERENT 
LATITUDES IN THE NORTHERN HEMISPHERE. 



102 CLIMATE. 

The gradual decrease of temperature which 
takes place, according to the elevation of land 
above the level of the sea, has a very beneficial 
effect in diversifying the climates over the earth's 
surface, and in adapting it to the growth and 
sustenance of an almost endless variety of plants 
and animals. In intertropical regions, districts 
which are situated near the level of the sea pos- 
sess an extremely high temperature ; and unless 
furnished with most copious supplies of rain, 
present a highly arid and parched aspect, like 
Peru ; but, on the contrary, if rain falls abun- 
dantly, they are covered with the most luxuriant 
vegetation, like the fertile lowlands of Guiana. 
At the elevation of 3000 or 4000 feet, the heat 
becomes less intense, and a change takes place 
in the productions of the soil. At that of 7000 
or 8000, the vegetation, and in great measure the 
climate, resemble that of temperate countries. 
At still greater elevations, the climate and plants 
are similar to those of arctic regions ; and at 
length the line of perpetual congelation is 
reached, where nothing meets the eye but bare 
rocks and accumulations of ice and snow. 

In warm latitudes, the snow-line is found to be 
higher on mountains which inclose or border on 
elevated table lands, than on isolated mountains, 
or on such as rise precipitously from low plains. 



CLIMATE. 



103 



This appears to be caused by radiation from 
the elevated plains; for these, having become 
heated during the day, radiate or part with this 
heat during the absence of the sun, and thus 
tend to maintain the temperature of the moun- 
tains in their vicinity during the night, whereas 
isolated mountains, being surrounded by the at- 
mosphere, part with heat, instead of receiving it, 
during the sun's absence. 

The Himalaya Mountains afford a striking ex- 
ample of the effect thus produced by an elevated 
table-land. On the southern side of that mighty 
range, in N. lat. 30, the mountains rise directly 
from a flat country, not more than 1000 feet 
above the level of the sea, covered with a close 
jungle, which tends to cool the superincumbent 
air ; and on this side of the mountains the height 
of the snow-line does not exceed 12,000 or 13,000 
feet. On the northern side of the same vast 
mountain range, the elevated table-land of Tibet 
extends, rising to the height of 15,000 feet above 
the level of the sea ; and in the vicinity of this 
great plain, the snow-line reaches the height of 
17,000 feet above the level of the sea. In very 
cold climates the reverse takes place : ice-covered 
table-lands have a tendency, by absorption of 
heat, to lower the temperture of mountains 
which are situated near them ; for the tempera* 



104 CLIMATE. 

ture of isolated mountains in icy regions is some- 
times found to be higher than that of the plains 
at their base. 

The nature of the soil produces some effect on 
the climate of any region. Sandy soils are sub- 
ject to become rapidly and intensely heated, and 
when the sun's rays are withdrawn, they rapidly 
radiate and part with the heat they have acquired, 
thus increasing the general temperature of the 
surrounding districts. Clayey soils ^ on the other 
hand, become slowly heated, and as slowly part 
with heat. Swampy ground chills the air, and 
extensive forests produce a similar effect; and 
thus, cultivation not unfrequently causes a 
change in the climate of a country ; for the 
draining of marshes and the clearing of dense 
forests may raise the winter temperature of a 
cold country, as has been effected in some parts 
of North America* whilst irrigation and the cul- 
ture of trees may tend to improve and moderate 
the climate of hot dry lands, as has been expe- 
rienced, though hitherto on a small scale, in 
some parts of California. 

The prevailing winds produce considerable 
effects on the climate of any region. Countries 
where the prevailing winds sweep across a wide 
expanse of ocean are not subject to extremes of 
heat and cold. Thus, the climate of the British 



CLIMATE. 



105 



Isles is moderated, because the most prevalent 
winds pass over the Atlantic Ocean. In the 
eastern portion of the New England States the 
south wind is marked for its warmth. This 
comes in from the Gulf Stream and the Ocean. 
Winds which traverse large tracts of land vary 
in character according to the nature of the sur- 
face over which they pass. Hence in the Atlan- 
tic States, the west and the north winds are dry 
and cold. 

The position of mountain ranges also produces 
considerable effect on the climate of any region, 
especially when elevated ridges extend from east 
to west, and thus either form a screen from the 
north, or leave a country unsheltered in that di- 
rection. Thus, the Carpathian Mountains screen 
Hungary from the cold blasts of the north, and 
consequently that territory enjoys a remarkably 
mild climate ; whilst Poland, which is situated 
to the north of that range, and therefore unpro- 
tected from those piercing winds, suffers from a 
very cold and humid climate. 

The currents of the ocean form very influential 
causes of the diversity of climate. The polar 
currents, as we have already seen, carry towards 
the tropics, not only vast streams of cool water, 
but also floating masses of ice, which tend in a 
great measure to lower the temperature of the 



106 



CLIMATE. 



regions near which their course extends. The 
Gulf Stream, on the other hand, traverses the 
Atlantic Ocean, carrying with it a high temper- 
ature, which it imparts to "Western Europe, and 
in all probability to the whole of the Northern 
Ocean. 

The waters of the Gulf Stream bear with them 
from the Gulf of Mexico large quantities of a 
species of sea-weed called sargasso; this accu- 
mulates (probably owing to the meeting of some 
currents) in a portion of the ocean lying between 
the 33d and 35th parallels of north latitude, and 
covers an area extending about 2000 miles from 
east to west, and 350 from north to south. 
The water in this tract of the ocean is nearly 
stagnant, and being continually supplied with 
fresh streams of water which have become 
heated in the Gulf of Mexico, its temperature 
is maintained to the height of from T to 10° 
above that of the Atlantic in the same latitude. 
This is called the Sea of Sargasso^ or the Re- 
cipient of the Gulf Stream^ and there appears 
reason to conclude, that this mass of warm 
water materially affects the climate of the re- 
gions to which its influence extends, both in 
Europe and North America. 

The causes which produce diversity of climate 
being so various, great difference of temperature 



CLIMATE, 107 

is found to prevail in similar parallels of latitude, 
and no rule can be laid down relative to the 
climates on the earth's surface. It may, how- 
ever, be considered that, generally speaking, the 
eastern districts of both the Old and New Con- 
tinents possess more excessive climates than the 
western districts of either ; that the climate in 
the interior of continents is more excessive than 
either; and that islands have a more equable 
or less variable temperature than large masses of 
land. 

In intertropical regions, comparatively little 
variation occurs in the temperature throughout 
the year; in some places there being scarcely 
more than four degrees between the average 
temperature of the warmest month and that of 
the coldest month. In temperate zones the dif- 
ference is usually much greater. Thus, in Lon- 
don, the mean summer temperature is about 63° ; 
and the mean winter temperature is about 39^-° ; 
the difference between the mean summer and 
winter temperature being twenty-three degrees 
and a half. In New York, the mean summer 
temperature is about 71°, and the mean winter 
temperature about 30°, making a difference of 
forty-one degrees. 

With the view of ascertaining the general dis- 
tribution of heat over the surface of the globe, 



108 CLIMATE. 

observations relative to the mean annual tem- 
perature of various portions of the earth have 
been made, and lines called isothermal lines, or 
lines of equal temperature, are traced on the globe, 
indicating the various points on the earth's sur- 
face where the same mean annual temperature 
has been observed to prevail. These lines do 
not coincide with the equator, or with the paral- 
lels of latitude, places possessing the same an- 
nual temperature being often situated in widely- 
different parallels of latitude. Thus, London 
and New York possess very nearly the same 
mean annual temperature, that of 51° ; but Lon- 
don is situated about eleven degrees further 
north than New York, and, as we have just seen, 
the summer and winter temperature of the two 
cities differs considerably. It is therefore evident, 
that though these isothermal lines convey a 
general idea of the distribution of heat over the 
earth^s suface, they do not determine the climates 
of the regions where the observations have been 
made. Lines indicating the mean summer and 
mean winter temperatures, called isotheral and 
isochimenal lines, when these shall have been 
carried out on the surface of the globe, may tend 
more fully to accomplish this object. 

The line of highest temperature, which is nearly 
83°, takes its course generally to the north of the 



ELECTRICITY AND MAGNETISM. 109 

equator, crossing the Isthmus of Panama, and 
passing through Africa at about the 11th paral- 
lel of latitude. The interior of the latter re- 
gion is considered as the hottest portion of the 
earth. 

The line of lowest temperature in the northern 
hemisphere, is not, as we should suppose, in the 
immediate vicinity of the North Pole, but com- 
mencing at Hudson's Bay, it crosses Greenland, 
bears somewhat towards the north, and after- 
wards declines to the central part of Siberia. 



XI. ELECTRICITY AND MAGNETISM. 

Electricity produces an infinity of changes in 
the natural world. It may be artificially elicited 
or called forth by friction, and then it is termed 
ordinary electricity ; or by the contact of certain 
substances, and the action attendant on this con- 
tact, and then it is called voltaic or galvanic 
electricity. 

All substances are supposed to contain a cer- 



110 ELECTRICITY AND MAGNETISM. 

tain portion of electricity, and if by friction, or 
any other means, any substance, acquires more 
electrical action than it would naturally possess, 
it is said to be positively electrified ; and if, on 
the other hand, there appears to be less electrical 
excitement than it would possess in its natural 
state, it is said to be negatively electrified. Sub- 
stances, when positively electrified, attract or draio 
towards them other substances which are in a 
state of negative electricity, or even those which 
are in a natural state ; but will repel or force 
from them substances which are positively elec- 
trified. 

The electrical state of substances is easily dis- 
turbed, and even without actual contact, any 
substance in a state of positive electricity may 
produce negative electricity in a substance near 
it. The sudden contact of bodies in an opposite 
state of electricity is attended with vivid light, 
called the electric spark, and accompanied by an 
explosion and shock. This is exhibited on a 
splendid but awful scale in the lightning's flash 
and the thunder clap. 

The earth is considered to be always in a state 
oi positive electricity, the air, when pure, to be in 
one of negative electricity. Atmospheric air, 
however, is subject to incessant variations, both 
as to the character and degree of its electrical 



ELECTRICITY AND MAGNETISM. Ill 

excitement, for it is liable to be affected by the 
evaporation and condensation of moisture, by 
the various chemical processes which are con- 
tinually carried on in the natural world, &c., and 
thus the electrical equilibrium of the atmosphere, 
or its natural electrical state, is subject to be dis- 
turbed. This equilibrium will be restored when 
an explosion has taken place, and hence it is that 
in peculiar states of the atmosphere, thunder 
storms act a beneficial part in restoring the air 
to a healthy condition, or, in other terms, restor- 
ing the electrical equilibrium. 

The intensity of electricity is greater during 
the day than at night, and also in summer than 
in winter ; and is considered to diminish from the 
equator to the poles. 

Electricity is perpetually effecting great changes 
in the earth's crust ; not perhaps so much in its 
loud and fearful displays, which are evident to 
man, as in its unseen quiet operations ; in very 
many instances unquestionably acting on the 
principle of voltaic electricity^ the electrical action 
in such cases being produced by long-continued 
electrical currents. 

Terrestrial ruagnetism may be regarded as a 
peculiar exhibition or state of electricity, and 
may be considered under two heads — viz., mag- 
netic direction^ and magnetic intensity. 



112 ELECTRICITY AND MAGNETISM. 

The magnetic power of the loadstone to attract 
iron or steel is well known ; if a bar of iron or 
steel be subjected to a continued current or 
stream of electricity, or even be allowed to re- 
main in contact with the earth in a vertical or 
upright position for a lengthened period, as old 
iron railings may have done, it acquires this 
magnetic power, or becomes magnetized. 

If a nicely-balanced bar or needle of magnet- 
ized steel or iron^ be suspended from its middle 
by a piece of untwisted silk, free to move in all 
directions, both horizontally and vertically, it 
will turn itself to one particular position, and if 
disturbed, it will invariably return .to the same 
position, pointing downwards to the earth at a 
particular angle, and also in a particular north- 
ward and southward direction. This is called 
the magnetic direction of the needle. If placed 
on a pivot, in a box or case, so as to confine it 
in a horizontal position, it will be found to as- 
sume the same regular northward and southward 
direction ; not due north and south, but north- 
ward and southward. At one period the mag- 
netic needle was supposed to point so truly to 
the poles of the earth, that the phrase, "true as 
the needle to the pole," has become a proverbial 
expression ; and hence the north and south ends 
of magnets were termed their north and south 



MAGNETISM. 113 

poles; and in fact it appears that in 1659 the 
needle actually pointed thus in London. 

It is on the above principle that the mariner's 
compass has been constructed, which was sup- 
posed to point invariably due north and south. 
It is now well known, not only that the mag- 
netic needle does not point due north and south 
in all parts of the globe, but that it does not 
permanently maintain the same direction at the 
same places. 

The present north magnetic pole, or point to 
which the needle is directed on this side of the 
equator, was found by Sir James Ross, in Ion. 
115° W. and lat. 70° N., north of Hudson's Bay. 
The magnetic pole of the southern hemisphere 
has not yet been ascertained with certainty, but 
is with great probability supposed to be in Ion. 
152° E. and lat. 72^ S. 

We have seen that the magnetic needle, if 
freely suspended, does not settle itself in a direc- 
tion parallel with the horizon, but dips or inclines 
downvmrds ; this is called its dip or inclination. 
This dip or inclination of the magnetic needle, 
like its declination, differs in different parts of the 
earth's surface, and, like that, has undergone 
considerable changes in its direction. 

The observation of navigators shows that 
there is a line encircling the earth, at every point 
8 



114 DISTRIBUTION OF PLANTS. 

of which the needle will take a true horizontal 
position. This is called the magnetic equator. It 
is not a great circle of the earth like the terres- 
trial equator, and its form and position are 
continually varying. 



Xn. GEOGRAPHICAL DISTRIBUTION OF PLANTS. 

Plants^ in an almost endless variety of forms, 
are spread over the surface of the globe, afford- 
ing sustenance to man, and to a vast number of 
the other creatures of God's hand. 

Some plants are adapted to thrive more par- 
ticularly in cold climates, or in mountain re- 
gions ; others attain the greatest perfection in 
temperate zones, and others belong exclusively 
to the hottest regions of the earth. Some plants 
will not flourish unless furnished with copious 
supplies of moisture, whilst others are so con- 
stituted that they can endure long-continued 
drought. Some plants prefer a clayey soil, oth- 
ers a chalky soil, others a sandy soil, whilst others 
grow in the crevices of rocks. Some plants are 
inhabitants of salt marshes^ some of fresh-water 
iakeSy some of running' streams, some of the 



CLASSIFICATION OF PLANTS. 115 

ocean, and some of the dark caverns of the earth. 
We thus find that each portion of the globe has 
its own appropriate vegetable productions, spe- 
cially adapted to its climate, its soil, and its 
elevation above the level of the sea. 

Plants are divided with respect to their flow- 
ers into two departments, J^?A6B?^c>g*»mow5 {ox phan- 
erogamous) and cryptogamous ; and the former of 
these, with respect to the structure of the plants, 
into two classes, endogenous and exogenous. 

PhsBnogamous plants are such as bear a 
plainly distinguishable flower. This class is 
found almost exclusively in the torrid zone, 
largely in the temperate, but scarcely at all in 
the frigid zones. 

The cryptogamous, or flowerless plants, called 
also a-cotyledonous, because they have no seed- 
leaf, are plants whose flowers and seeds are 
either so minute as to be scarcely discernible, or 
are altogether concealed from our view. This 
class ranks as the lowest in the scale of vege- 
table productions, and includes lichens, mosses, 
the fungous tribes, ferns, algce or sea-weeds, &c. 

Endogenous plants are so called because their 
growth or increase takes place from within, and 
also mono-cotyledonous, because when their seeds 
germinate they have only one seed-lobe or leaf, as 
may be observed in the springing up of grass, 



116 DISTRIBUTION OP PLANTS. 

which belongs to this plass ; it also includes 
wheat, rye, barley, rice, maize, lilies, palms, &c. 
In the divisions of the flowers and fruit of the 
plants belonging to this class, the number three^ 
or its multiple^ prevails. Of this the lily forms an 
example, which has twice three (or six) petals. 

Exogenous plants^ which form the highest class 
in the vegetable world, are so called because 
their growth takes place externally^ that is, at or 
near the surface, and outside of the pith. The 
yearly increase in some trees is so distinctly 
marked in rings or circles, that their age can be 
nearly determined. Plants of this class are also 
called di-cotyledonous^ because they have two 
seed-lohes or seed-leaves^ as may be seen in 
the mignionette, the laburnum, &c., which be- 
long to this class. The number five generally 
prevails in the division of the parts of the flow- 
ers in this class. This class includes a large 
proportion of the trees of the forest, and also 
most of the flowering shrubs and herbs. The 
oak, pine, elm, ash, beech, poplar, chestnut, wal- 
nut, &c., belong to this class, as do also the rose, 
mallow, heath, daisy, pea, cabbage, &c. &c. 

The number of different kinds of exogens^ or 
exogenous plants^ is far greater than that of en- 
dogens, or endogenous plants. In tropical regions 
the proportion is about four to one, and in tem- 



CLASSIFICATION OF PLANTS. 117 

perate zones about six exogens to one endogen. 
In the arctic regions, the proportion is not above 
two to one, but in these regions, forest trees 
are few in number and dwarfish in growth ; and 
cryptogamic plants are very abundant. 

Some plants are perennial^ that is, live for a 
greater or less term of years, some species at- 
taining a very great age. The oak appears to 
arrive at perfection at about the age of sixty 
years, but lives for a much longer term ; yew 
trees are much longer lived than the oak. Some 
plants are annual, springing up, producing flow- 
ers and fruit, and decaying in one short season. 
Other plants are biennial, usually only sending 
forth stems and leaves in the first year, and per- 
fecting their flowers and fruit in the following 
season. 

Some plants are deciduous, or cast their leaves 
in the autumn, and renew them in the spring ; 
others are evergreen, and never destitute of foli- 
age. The temperate zone may be considered as 
more especially the region of deciduous trees. 
The never-ceasing energy with which vegetation 
proceeds in intertropical regions imparts to the 
plants of those climates a luxuriance unknown 
in the temperate zone, and at no time are the 
trees bare of leaves ; a screen being thus afforded 
to the inhabitants of those regions, at all seasons 



118 



DISTRIBUTION OF PLANTS. 



of the year, from the scorching rays of the sun. 
The evergreen trees of the cold regions of the 
earth are of a totally different character, con- 
sisting chiefly of pine and fir trees, whose needle- 
shaped leaves are adapted to withstand the 
rigors of a northern winter, and whose thick 
foliage, often sustaining a mass of snow, forms 
a shelter both to man and to animals from the 
severe and long-continued cold. 

Plants derive their nourishment from the at- 
mosphere and from the earth. The leaves of 
plants constantly imbibe both moisture and car- 
bonic acid gas from the atmosphere, during the 
hours of daylight, and more particularly of bright 
sunlight. Carbonic acid gas is a compound 
of carbon and oxygen ; this carbonic acid gas 
the green parts of plants have the power of de- 
composing^ or of separating into its two component 
parts of carbon and oxygen ; the carbon enters 
into their composition, and the oxygen is re- 
turned pure into the atmosphere. As plants 
possess less energy in the shade, or in dark 
gloomy weather, they have not, under such cir- 
cumstances, power to decompose the whole 
amount of carbonic acid they imbibe, and a 
certain portion of carbonic acid as well as of 
oxygen is given out by the leaves. At night 
they no longer emit pure oxygen, but, on the 



GROWTH OF PLANTS. 119 

contrary, return a portion of the carbonic acid 
into the atmosphere. Carbonic acid gas is 
deleterious both to man and animals, and 
hence it is that plants in our apartments, if 
placed in the full light, are healthful, but are 
likely to prove injurious at night. 

The carbon thus derived from the atmosphere 
enters into the composition of plants, and forms 
their solid parts ; they also imbibe ammonia from 
the atmosphere, the latter (which is a compound 
of nitrogen and hydrogen) appearing to be es- 
sential for the perfection of the flowers and fruit. 
The roots suck up both carbonic acid and am- 
monia, as well as moisture, from the soil ; from 
whence they also derive potash^ soda^ lime, silica 
or flint J and various other substances, which 
give to vegetables their hardness. Thus, to bring 
wheat to perfection, it requires a supply of 
moisture and carbonic acid to promote the 
growth of the blade ; silica to give the culm or 
stem its hardness and firmness ; and ammonia 
or nitrogen for the nourishment of the grain ; 
and, above all, the sun's rays to give energy to 
the whole, for wheat will not succeed in regions 
where the mean summer temperature is below 
57° or 58°. 

, Intertropical America is no less distinguished 
for the splendor and luxuriance of its vegetable 



120 DISTRIBUTION OF PLANTS. 

productions than for their variety^ the number of 
plants which are natives of that portion of the 
globe being more than double that of those 
which are indigenous to, or natives of, Europe. 
The whole of Asia and its islands possess a 
smaller number than Europe ; Oceanica, in- 
cluding Australia, New Zealand, and the islands 
in the Pacific Ocean, less than Asia ; and Africa 
(as far as hitherto explored) a smaller number 
than any other portion of the globe of similar 
extent. 

Some species of plants are met with only in 
very limited districts, to which they appeared to 
be wholly confined ; thus the Irish yew appears 
to grow naturally nowhere except in Ireland. 
Other plants have a much wider range ; thus 
the Scotch fir is met with not only in Scotland, 
but in various other regions possessing a nearly 
similar climate. It however appears that, gen- 
erally speaking, particular kinds of plants form 
the prevailing vegetation in certain portions of 
the earth's surface, and, accordingly, botanists 
have attempted to divide it into botanical re- 
gions^ each region being named from the prepon- 
derance of certain plants. Thus the southern 
portion of the United States is called the Region 
of Magnolias^ because that plant grows in re- 
markable abundance and to a splendid size in 



DISTRIBUTION OF PLANTS. 121 

those regions. The lowlands of Mexico and of 
some adjacent countries are called the Region 
of Cacti, from the preponderance in those dis- 
tricts of the cactus tribe of plants. 

We have seen that a similarity exists between 
the temperature of land near the level of the sea 
in high northerly and southerly latitudes and that 
of elevated mountains in hot climates. We also 
find that a remarkable correspondence occurs 
between the plants which are natives of regions 
bordering on perpetual snow (and, therefore, 
possessing nearly similar climates) however re- 
mote they may be from each other, or however 
different may be their elevation above the level 
of the sea. The temperature of the middle re- 
gion of mountains in equatorial regions usually 
approaches that of temperate zones, and the 
plants growing in those respective regions usu- 
ally bear much resemblance, though they by no 
means exhibit so great a similarity as those of 
frigid regions. The flora, or assemblage of 
plants, in equatorial regions, may be considered 
as peculiar to those portions of the globe. 

Baron de Humboldt divides the surface of the 
earth into eight zones of vegetation, which are 
named from the prevailing plants of each zone 
or region. 

1. The equatorial zone, or region of palms and 



1^ DISTRIBUTION OF PLANTS. 

bananas, which extends to about 15° on each side 
of the equator, and corresponds to about 3000 
feet above the level of the sea under the equator. 
The vegetation in this region consists of dense 
forests, which never lose their foliage, and to 
which the preponderance of palm trees imparts 
a peculiar character. The luxuriant and lofty 
trees are interlaced and overtopped by gigantic 
creeping plants, or covered with singularly- 
formed orchidaceous plants, which derive their 
sustenance from the atmosphere. 

2. The tropical zone, or regions of tree-ferns 
and Jigs, extending from about latitude 15° to 
the tropics. Tree-ferns do not arrive at their 
greatest perfection at the level of the sea under the 
equator, their range being from about 1300 feet 
to 5000 feet above the level of the sea. In the 
South Pacific Ocean, owing to the more equable 
climate of that portion of the globe, tree-ferns 
succeed in much higher latitudes, these trees 
being very prevalent in the forests of New 
Zealand. 

3. The sub-tropical zone, or region of laurels 
and myrtles : from the tropics to about 34°. 

4. The warm temperate zone, or region of ever' 
green trees : from 34° to 45°. 

5. The cold temperate zone, or region of de- 
ciduous trees : from 45° to 58^^. 



BISTRIBUTION OF PLANTS. l23 

6. The subarctic zone, or region of pines : from 
5S° to the arctic circle. 

7. The arctic zone, or region of andromedas 
and alpine rhododendrons : from the arctic circle 
to 72°. 

8. The polar zone, or region of alpine plants 
(gentian, ranunculus, &c.) : from 72° to the far- 
thest limits of vegetation. In this region lichens 
and mosses are very numerous. Alpine plants 
grow under the equator to the elevation of 
12,000 or 13,000 feet above the level of the sea. 
Owing to local peculiarities, some species grow 
at still greater elevations in the Himalaya moun- 
tains, springing up as the snow melts^ at the 
height of more than 16,000 feet. 

In the temperate climate of Europe the ef- 
fects produced by elevation above the sea level, 
though less striking than in equatorial regions, 
are nevertheless of great importance. Thus, in 
the lowlands of Italy and Sicily, and the south of 
Spain, palms and other plants of the warm re- 
gions of the earth come to perfection ; these are 
succeeded by the orange, the fig, and the olive ; 
the two latter of which thrive in the southern 
valleys of Switzerland, but do not succeed be- 
yond 1000 feet above the level of the sea. In 
the latter region, the vine may be successfully 
cultivated to the elevation of 1600 feet: the 



124 DISTRIBUTION OF PLANTS. 

walnut to 2400 feet ; and the chestnut to nearly 
8000 feet. .The range of the oak, ash, and ma- 
ple, extends to about 3800 feet ; that of the larch 
to about 6000 feet ; of the pine to 6800 feet ; and 
of the spruce fir to 7400 feet, which is about 
2000 feet below the snow-line in that region. 
Beyond the region of trees, heath and furze, in- 
terspersed with some low shrubs, form the prin- 
cipal occupants of the soil, though abundance of 
valuable alpine grass is met with in some parts. 
At still greater elevations, lichens and mosses 
grow in the crevices of the otherwise bare rocks ; 
and, even beyond the line of perpetual congela- 
tion, the singular vegetable production called 
the palmella nivalis^ or red snow, which occurs 
abundantly in the arctic regions, is occasionally 
found amid the perpetual snow of Mont Blanc. 

An acquaintance with the various zones and 
elevations above the sea-level, at which plants 
of utility to man will succeed, is of extreme 
importance to all settlers in newly-colonized 
countries ; for, as it would be a vain attempt 
to introduce into England plants adapted to 
flourish only in hot climates, so would it lead to 
disappointment were we to cultivate in inter- 
tropical regions such as will only thrive in tem- 
perate zones, in cold regions such as require a 
high summer temperature, or in dry regions 



DISTRIBUTION OF PLANTS. 125 

such as require abundance of moisture. Now, 
wheat will not succeed at or near the level of the 
sea in intertropical regions, nor will it come to 
perfection in climates where the summer tem- 
perature is below 57° Fahrenheit. It, however, 
may be cultivated with great success, even un- 
der the equator, between the elevations of 4500 
and 10,000 feet above the level of the sea. Its 
northern or polar limits in North America have 
scarcely yet been determined ; its successful cul- 
tivation does not extend beyond N. lat. 58° in 
the British Isles, but reaches to lat. 64° in Nor- 
way, though in Sweden not beyond 62°, and in 
Russia not much beyond N. lat. 60°. The suc- 
cessful cultivation of oats extends to the north- 
ern extremity of the British Isles, and that of 
barley to Faroe Isles. 

The great practical utility of this department 
of Physical Geography will be evident to all ; it 
will also be readily conceived that a further 
pursuit of the subject must lead to great gratifi- 
cation. And in truth, the more our attention is 
directed to it, the more shall we be convinced 
that " The Lord God has made to grow every 
tree that is pleasant to the sight, and good for 
food." 



126 DISTRIBUTION OF ANIMALS. 



XIII. GEOGRAPHICAL DISTRIBUTION OF ANIMALS. 

The distribution of animals over the surface 
of the globe is, like that of plants, greatly influ- 
enced by climate and temperature. Animals 
also, like plants, belong to particular regions, or 
have their natural stations and habitations^ though, 
since a considerable number of animals possess 
the power of transporting themselves from one 
region to another, these cannot in all cases be so 
determinately fixed. 

The animal kingdom has been arranged in four 
great departments : I. Vertebrata, or vertebrated 
animals ; II. Articulata, or articulated animals ; 
III. Mollusca, or molluscous animals ; and IV. 
Radiata^ or radiated animals. 

The vertebrated animals are so named from 
the bones of the neck, which are called vertebrce. 
Animals belonging to this department all possess 
a skull and a back bone ; they have organs of 
sight, hearing, smell, and taste ; and have never 
more than four limbsj though in some classes of 
animals these limbs are not so perfectly devel- 
oped as in others. This division includes man^ 
quadrupeds^ birds, serpents, frogs, tortoises, croco- 



CLASSIFICATION OF ANIMALS. 127 

diles^ and such fish as cod^ herrings, &c., all of 
which have a bony skeleton. 

This department of the animal kingdom is 
divided into four classes : 1, mammalia, or animals 
which suckle their young, such as man, the cow, 
bat, whale, &c. ; 2, birds; 3, reptiles, such as 
serpents, turtles, frogs, the crocodile, &c. ; 4, fish, 
that is, such fish as possess a bony skeleton. 

The articulated animals are so named from 
articulus, " a little joint," on account of their pe- 
culiar formation, which consists of a head and 
successive portions jointed together. To this 
division belong the insect tribes, the earthworm., 
crustaceous animals or Crustacea (such as lob^ 
sters, crabs, shrimps, &c.). Some articulated 
animals have jointed limbs attached to the side 
of the body, like the fly, centiped, lobster, &c. 

The molluscous animals are so named from 
mollis, " soft," because their bodies are soft and 
are without a bony skeleton. Many molluscs 
have shells forming a covering and defence for 
their soft bodies ; the oyster, snail, &c., possess 
these protecting shells : others are destitute of 
this covering ; of this we find instances in the 
common garden slug, the cuttle-fish, &c. 

The radiated animals form the fourth great 
division of the animal world. They are called 
radiated, because in the greater number of the 



128 DISTRIBUTION OF ANIMALS. 

animals belonging to this division, the organs of 
motion and sense are considered to radiate from 
a common centre, like the petals or flower-leaves 
of a daisy or anemone. To this division belong 
the coral animal, the sea-anemone, &c. Animals 
of this division are also termed zoophytes, from 
zo-on, " animal," and phyton, " a plant," because, 
though in fact they are living creatures, they 
sometimes bear a great resemblance to plants 
in their structure. 

When animals are identical in their anatomi- 
cal structure, they are considered to belong to 
the same species. When two or more kinds of 
animals are very nearly alike in their structure, 
though with some differences, they are consid- 
ered to belong to the same genus (jpluxdl genera). 
When the differences are greater, they are ar- 
ranged into a group, called an order. And 
when only a few points of resemblance can 
be traced, they are regarded as belonging to 
the same class. A department contains several 
classes. Thus, the dog belongs to the depart- 
ment vertebrata, to the class mammalia, to 
the order carnivora, to the genus canis, and to 
the species dog. Different systems of classifica- 
tion vary the names of the orders of mammalia. 
One system gives three orders, the carnivora, 
herbivora, cetacea; another gives as many as 



DISTRIBUTION OF ANIMALS. 129 

twelve. Among some species, we also meet 
with varieties ; thus the varieties of the dog are 
the mastiff, greyhound, terrier, &c. 

The same species of animals are not met with 
in all parts of the world, and even some genera 
are found to be peculiar to particular regions. 
Thus, the royal lion is met with only in Africa, 
the Asiatic lion being of a different species and 
of a smaller size. The tiger is peculiar to Asia 
and some of the Asiatic islands ; the giraffe to 
Africa ; the elephant is found in Africa and in 
some parts of Asia, but the African and Asiatic 
elephants are of different species. 

The animals of the Old World generally differ 
in species from those of the New World. Thus, 
besides those we have already enumerated, the 
ape and baboon, the hyaena, panther, rhinoceros, 
hippopotamus, horse, ass, camel, buffalo, croco- 
dile, python, &c., are all inhabitants of the Old 
World. 

The puma (sometimes erroneously called the 
American lion), the jaguar, the sloth, armadillo, 
bison, lama, aUigator or cayman, boa con- 
strictor, rattlesnake, &c., are all peculiar to the 
New World. 

In the most northerly parts of both continents 
alone are the same species of animals found ; 
thus, the Polar bear and the iVrctic fox inhabit 
9 



130 DISTRIBUTION OF ANIMALS. 

the whole of the icy regions extending from 
Spitzbergen- and Siberia to Arctic America ; 
these animals being capable of enduring the 
severe cold of those high latitudes, and of trav- 
ersing the frozen surface from one continent to 
the other. 

The annals of a country, taken collectively, 
constitutes its fauna. That of Australia in- 
cludes some very singular forms. Among these 
are the various species of opossum and kangaroo, 
the ornithorynchus, or duck bill, &c. The flying 
squirrel, or flying cat, is found in Australia and 
some islands in the Indian Ocean. Bats of vari- 
ous species are met with in almost all the warm 
and temperate regions of the earth. 

Birds, like other animals, have their natural 
geographical limits ; and though some have a 
very wide range, others are confined to particular 
regions ; thus, the birds of paradise are found 
only in New Guinea and some adjacent islands ; 
the beautiful sun birds are confined to Africa, 
and the humming birds are peculiar to the New 
World. The powers of flight possessed by most 
birds, and the migratory instinct which leads 
some species of birds to remove their quarters at 
the change of season, cause them to possess a 
very wide range, and to enjoy at all times a 
climate especially adapted to their wants. 



DISTRIBUTION OF ANIMALS. 131 

In the animal as well as in the vegetable king- 
dom, the largest number of species is met with 
in the warm regions of the globe, and a gradual 
decrease, in the number both of genera and spe- 
cies, takes place as we recede from the equator. 
It is in intertropical regions also, that mammife- 
rous quadrupeds are most remarkable for their 
magnitude, strength, and ferocity ; that reptiles 
are larger and more venomous ; that birds are 
decked with the most splendid plumage, and the 
insect tribes distinguished for then size and the 
brilliancy of their tints. These effects of light 
and heat appear to be extended even to the in- 
habitants of the ocean ; sharks and some other 
fish are larger and more ferocious in the seas of 
tropical regions, and some species of fish are 
adorned with gayer colors, than those of temper- 
ate zones. It is also from the warm regions of 
the earth, that the greater number of the most 
beautiful shells of molluscous animals are ob- 
tained, and there, likewise, do the coral animals 
and other radiata occur in the greatest variety 
and abundance. 

Animals, like plants, are adapted for the sta- 
tions or situations in which Creative Wisdom 
has placed them ; and thus we find animals be- 
longing to cold climates provided with warm 
furry coats, which would be unsuited for the 



132 DISTRIBUTION OF ANIMALS. 

inhabitants of hot regions. Sometimes, when 
animals of the same species inhabit countries 
possessing different climates, the garb of the one 
will differ from that of the other, in accordance 
with the difference of climate. Thus, the skin of 
the stoat in England is comparatively thin, and 
of a dull grayish brown color ; but in northern 
Russia and Siberia, the coat of the animal is 
transformed into a beautiful thick fur, of a clear 
white in every part except the tip of the tail, 
which is of a deep black, affording, under this 
form, the well known fur called ermine. 

If by accident, or the agency of man, animals 
are removed to places uncongenial to their na- 
tures, they either perish altogether, or some 
change takes place to fit them for their new 
abode. Thus, the race of sheep now inhabiting 
some of the valleys of intertropical South Amer- 
ica, which were originally transported from tem- 
perate European regions, possess, instead of 
their warm woolly fleeces, a coat of glossy hair, 
better adapted to the heat of the climate in 
which they have now become naturalized. Thus, 
again, a species of dormouse, which is a native 
of the warmer regions of the earth, does not in 
its natural habitation, where it can at all seasons 
of the year obtain abundance of food, become 
torpid, or hyhernate ; but if removed to England, 



DISTRIBUTION OF MAN. 133 

/ 

where its means of subsistence fail during the 
winter, it acquires the habits of the English 
dormouse, and passes that season in a state of 
torpidity. 



XIV. GEOGRAPHICAL DISTRIBUTION OF MAN. 

The geographical distribution of man forms a 
subject of totally different character from any 
that has hitherto engaged our attention. Instead 
of speaking of genera and species, we have now 
to direct our inquiries to the diversities of lan- 
guage, and the varieties of form and color, in the 
human race, and to the distribution over the 
earth's surface of these diversities and varieties. 

The number of languages at present spoken in 
the world, is estimated at not much less than 
2000 ; but many of these appear to be derived 
from one common root or origin. Thus, the 
Hebrew, the Babylonian, Syrian, Arabian, and 
Abyssinian, are considered to have one common 
origin. They are collectively called Semitic, from 
Shem, the son of Noah, from whom the nations 
speaking these languages are supposed to have 
descended. This is called d^ family of languages. 



134 



DISTRIBUTION OF MAN. 




DISTRIBUTION OF MAN. 135 

Another family of languages, which is called 
the Indo-European, includes a large number of 
the languages or idioms of Europe and Asia. 

1. The Sanscrit, and all its dialects in India. 

2. The ancient Zend, or Medo-Persic language, 
and all the idioms now spoken in Persia and 
Armenia. 3. The Greek and Latin languages. 
4. The Sclavonian. 5. The Gothic or Teutonic. 
6. The Celtic. 

The languages of some nations, though not so 
distinctly traceable to the same origin, are often 
found to bear a great resemblance to each other, 
and they are then considered to belong to the 
same school or class of languages. Such are 
those termed monosyllabic^ from their consisting 
of words of one syllable. To this class belong 
the languages of China, Thibet, Siam, and 
nearly all the Indo-Chinese countries. 

Another class of languages is those termed 
poly synthetic. These consist of long words of 
many syllables, and very elaborate in their con- 
struction. To this remarkable class of languages 
belong all the numerous dialects or idioms of 
both North and South America. 

A dispersion and separation into famihes and 
tribes having taken place at an early period of 
man's history, considerable differences in the 
features and the color of the skin appear before 



136 DISTRIBUTION OF MAN. 

long to have become hereditary in certain tribes 
or nations, probably occupying comparatively 
remote regions of the earth. These peculiarities 
having formed permanent distinctions, natural- 
ists have attempted to class the human species 
into certain races or varieties^ according to the 
color of the skin and the form of the skull. 

The three leading divisions are the Caucasian, 
the Mongolian, and the Ethiopian races : to 
which may be added, the Malayan and the 
American races. 

The Caucasian, or White race, is characterized 
by a fair skin, sometimes with color in the cheeks, 
an oval face and expanded forehead, eyes vary- 
ing from blue to dark brown ; nose thin and 
slightly aquiline or straight, small mouth, and a 
full and rounded chin ; soft hair, varying in color 
from black to light brown and flaxen, and wav- 
ing or slightly curled. 

The most refined and civilized as well as most 
powerful nations of the earth have belonged to 
the Caucasian race ; and it is in the regions in- 
habited by this race, that both the Semitic and 
Indo-European languages have prevailed, and 
do still prevail. The ancient and modern inhab- 
itants of the regions bordering on Mount Cauca- 
sus, the higher castes of India, the Afghans, the 
Medes, Persians, and Arabs, the inhabitants of 



DISTRIBUTION OF MAN. 137 

Northern Africa, and the Jewish people, all 
belong to this race. 

In Europe, the Caucasian race includes the 
ancient Greeks and Romans, and the present 
inhabitants of Greece, Italy, France, and other 
nations which derive their language and descent 
from the Greeks and Romans ; the Sclavonians, 
who occupy Russia, Poland, and parts of Austria 
and Turkey ; the Teutonic or Gothic tribes, who 
occupy Norway and Sweden, Denmark, Holland, 
Germany, Prussia, parts of Belgium, Austria and 
Switzerland, and a large portion of the British 
Isles ; and the Celtic race, who inhabit the north- 
western districts of Scotland, the west of Ireland, 
Wales, and some parts of Cornwall. This race, 
intermixed with the descendants of the ancient 
Romans, is also spread over Belgium, France, 
Switzerland, Italy, Spain, and Portugal. 

We thus find that the Caucasian race inhabits 
the whole of Europe, with the exception of Lap- 
land, Finland, and part of Hungary ; a large 
portion of the south-western regions of Asia ; the 
northern part of Africa, from about N. lat. 20° 
to the borders of the Mediterranean Sea; and 
through European colonists, a considerable por- 
tion of America, and of various other regions of 
the globe. 

The Mongolian race is characterized by a yel- 



138 



DISTRIBUTION OF MAN. 



lowish or olive-colored skin, a broad and flat- 
tened face, with a low and narrow forehead ; 
small blpick eyes obliquely set, a wide mouth 
and thick lips ; black hair, lank and thin. The 
Mongolian race at the present day occupies a 
large portion of Asia, to the north and east of 
the Himalaya Mountains. The nomadic or wan- 
dering Mongolian and Kalmuc tribes belong all 
to this race; as do also the Chinese, the Sa- 
moieds, and the inhabitants of Kamschatka. 
This race also occupies Finland, Lapland, 
Greenland, and part of Hungary, though in the 
last territory the characteristic features of the 
Mongolian race are much less strongly marked. 

The Ethiopi'an or Negro race is characterized 
by a black or very dark skin ; a narrow com- 
pressed skull, a low and narrow forehead, black 
eyes, a flat broad nose ; thick lips, especially the 
upper lip ; a small chin ; woolly, crisp, coarse hair, 
collected into little knots. This race is consid- 
ered to occupy nearly the whole of Africa to the 
south of the Great Desert ; parts of Madagascar, 
Australia, and New Guinea ; and some of the 
islands included in the Indian and Polynesian 
groups. 

The Malay or Malayan race bears much re- 
semblance to the Mongolian, though in the Ma- 
layan race the color of the skin is darker, and the 



DISTRIBUTION OF MAN. 139 

face less broad. This race occupies the Malay 
Peninsula, and a large portion of the islands of 
the Indian Archipelago. 

The American race is characterized by a red- 
dish colored skin ; by a high and receding fore- 
head, with generally regular features, and a 
rather prominent and frequently aquiline nose. 
This race, though fast diminishing from the face 
of the earth, includes the aboriginal inhabitants 
of the whole American continent. All the tribes 
occupying that vast range of country speak dia- 
lects or tongues allied to each other and belong- 
ing to that singular class which is formed of 
long polysyllables. The number of different 
dialects in America is estimated at no less than 
1500. 

The diversities of language on the face of the 
globe tend to the disunion of man from his fel- 
low man : and undoubtedly we must look to 
the spread of the Gospel, as the sole efficient 
means of restoring union among mankind, and 
of leading all the different members of the human 
race to feel that they belong to one great family, 
that they are all brethren, and children of one 
Father. It may be little that we individually 
can do to promote this grand object, but we 
may endeavor to perform our part. By the 
acquirement of foreign languages, we may be 



140 



DISTRIBUTION OF MAN. 



better enabled to meet every man as our brother ; 
and by the exercise of kindly feelings, and the 
mutual interchange of good offices, not only 
amongst our kindred and our countrymen, 
but amongst strangers and foreigners from 
every part of the globe, we may be instrumental 
in promoting " peace on earth, good-will towards 
men." 



141 



EXERCISES POR THE EXAMINATION OF PUPILS. 



I. The Objects of Physical Geography, (p. 1.) 

What is meant by Physical Geography ? — Why is it called 
Physical or Natural Geography ? — What advantages may result 
from its pursuit ? 

II. The Earth, (p. 2.) 

To what group of bodies does the earth belong ? 

What is the form of the earth ? — Mention three different 
modes by which the rotundity of the earth may be proved. 

How is the earth or globe divided into two parts ? — How are 
maps of the world frequently divided ? 

What is the circumference of the earth ? — What is its diame- 
ter from east to west ? — What from north to south ? 

Give some account of the earth's turning on its axis ; or of its 
diurnal motion. — Also of its motion in its orbit. — How is the 
earth placed in its orbit ? and what is the consequence of this 
position ? — Relate some particulars about mid-summer and 
mid-winter. 

m. Latitude and Longitude, (p. 9.) 

How is the earth or globe divided for the convenience of mea- 
surement? — How is latitude marked? and how many degrees 
of latitude are there ? — From what is latitude reckoned ? — 
What is meant by high and low latitudes ? —How are degrees 
subdivided? — How many miles are there in a degree of lati- 



142 EXERCISES FOR EXAMINATION. 

tude ? — What is meant when it is said that places are on the 
same parallel of latitude ? 

How is tl}e earth divided by circles running parallel with the 
equator ? — Mention the zones into which these divide the earth ; 
also the parallels of latitude to which they extend ; and for what 
cause particular names have been given to these zones. 

How is longitude determined? and from what is it reck- 
oned ? — How many degrees of longitude are there ? — Give some 
particulars about the number of miles contained in degrees of 
longitude j and their difference in different latitudes. — What is 
the length of a degree of longitude on the parallel of London ? — 
Give the meaning of the terms east and west longitude. — When 
are places said to be on the same meridian ? — What is meant 
when we speak of the sun's being on the meridian ? 

rV. Distribution of Land and Water, (p. 14.) 

What is the estimated proportion of land to water on the sur- 
face of the globe ? — What in the northern and southern hemi- 
spheres ? 

Under what general heads may the dry land be considered ? — 
Give an account of the two great continents. — Why are they 
called the old and new continents ? 

Describe islands. — Mention the largest island on the earth's 
surface. — What regions are included under the appellation 
of Oceanica ? 

How is the land arranged in the eastern, and in the western 
continent ? — Mention the direction of the greatest extension of 
land in the two continents. 

V. Variations of the Surface, (p. 17.) 

Describe the variations of the earth's surface. — Mention the 
usual arrangement of mountains. 

Give some account of mountain ranges. — What direction do 
they usually appear to take ? 



EXERCISES FOR EXAMINATION. 143 

Give the names of the principal mountain ranges which extend 
across the old continent. — Give the names of the mountain 
ranges which extend from north to south in the new continent. 

How are mountain ranges frequently disposed, in peninsulas 
and islands ? 

Give some particulars about the appearance and form of moun- 
tains, and about glaciers. — Describe mountain branches, and 
spurs. — What are detached or isolated mountains ? — Where are 
the loftiest summits usually met with ? — Give the heights of the 
principal mountains. 

Describe table-lands, or plateaus. — Mention the most remark- 
able plateau or table-land in Europe. — Mention table-lands in 
Mexico, in the Andes, and in Asia. 

Describe plains or lowlands. — Mention the most remarkable 
in Europe ; in Asia ; and in Africa. — Describe the lowlands of 
North and of South America ; and mention by what names they 
are distinguished. 

What are the various kinds of valleys ? — Describe principal 
valleys ; lateral or transverse valleys ; and subordinate valleys. — 
Describe basin-shaped valleys. — Give the various terms applied 
to narrow valleys ; and for what cause some of these terms have 
been applied. 

What forms the standard by which all the undulations of the 
earth's surface are measured ? 



VI. Geology, (p. 33.) 

What is Geology ? — What is meant by the earth's crust ? — 
Of what does the earth's crust consist ? — Mention the various 
kinds of rocks. — State also the meaning of the term fossil; and 
give some particulars about the general diffusion of fossils in all 
parts of the earth's crust. 

Describe earthy formations ; also pebbles, gravels, shingles, 
and boulders. — What is conglomerate, or pudding-stone ? — 
What is breccia ? 



144 EXERCISES FOR EXAMINATION. 

Mention the most abundant earths. — In what mineral sub- 
stance is silex found in a pure state ? — In what form is lime 
usually met with ? — What useful property does clay possess ? 

How are rocks classed ? — What are stratified or sedimentary 
rocks ? — How do they seem to have been formed ? — How are 
stratified rocks arranged ? and how is their relative age de- 
termined ? 

By what means are the lower rocks sometimes brought to the 
surface ? — Give the meaning of the term " crop out." — Men- 
tion the advantages which may result from this. 

What are unstratified rocks .•• — Mention the apparent mode 
of their formation ; and name the principal rocks of this kind. 

Into what three classes are unstratified rocks divided ? — De- 
scribe plutonic rocks. — State under what circumstances they 
are supposed to have become consolidated. — Describe trap rocks. 

— Mention the principal rocks of this class. — Describe volcanic 
rocks. — Mention the principal products of active volcanoes. 

In what regions of the earth do the most remarkable active 
volcanoes occur ? — How may volcanic eruptions prove beneficial ? 

— Give some account of a tremendous eruption in Iceland. — 
State the apparent connection between earthquakes and volcanic 
eruptions. 

What effects are sometimes produced by earthquakes ? — Do 
earthquakes occur in regions remote from active volcanoes ? 

Give some account of extinct volcanoes. — Describe intrusive 
rocks, and metamorphic rocks. — Give an instance of a trans- 
formed rock? 

What are dislocations or faults ? — What benefit results from 
faults ? — What do fissures sometimes contain ? 

Give some particulars about metallic veins. — Where is gold 
usually found ? — Where are copper, tin, lead, silver, and iron 
usually found ? 



EXERCISES rOR EXAMINATION. 145 



Vn. The Waters oe the Globe, (p. 45.) 

Under what heads may the waters of the globe be considered ? 

From what do springs take their rise ? — How are internal 
reservoirs supplied with water ? — What does spring water con- 
tain ? and what forms the distinction between soft water, hard 
water, and mineral water ? 

How may mineral springs be classed ? — Describe acidulous 
springs. — Describe chalybeate springs. — Describe sulphureous 
springs. — Describe the two kinds of saline springs. — Describe 
calcareous springs ; and give some account of their mineralizing 
or petrifying properties. — Describe stalactites and stalagmites. 
— Describe siliceous springs. 

Are thermal or hot springs of frequent occurrence ? — Describe 
the two kinds of hot springs. — Give some particulars about the 
temperature of the earth at various depths ; and mention by what 
means this has been ascertained. — Which kind of springs has 
usually the highest temperature ? — Name some remarkable hot 
springs. — Describe bituminous springs. 

From whence do rivers dei'ive their supplies of water ? — What 
is meant by the term water-shed ? — What constitutes the basin 
of a river ? — Give the area of the principal river-basins. 

On what does the velocity of a river in great measure depend ? 
— Describe cataracts, cascades, and rapids. — Describe deltas ; 
and estuaries. — What is meant by the bore? — Give some 
particulars about flood-seasons, or freshets. — What is the num- 
ber of considerable rivers in the Old World ? — What in the 
New ? — Give the length, situation, and termination of the prin- 
cipal rivers. 

Give some account of the various kinds of lakes. — Describe 
lakes at the sources of springs ; lakes in the course of a river ; 
lakes in depressions of the earth ; lakes in the craters of extinct 
volcanoes ; periodic lakes. — Mention the largest lake in Eng- 
land J the largest lakes in Europe ; in Asia ; in North America. 

What advantages result from the great extent of the ocean ? 
10 



146 EXERCISES FOR EXAMINATION. 

— Does the ocean form one vast mass of waters ? — Give its geo- 
graphical divisions. — Describe branch or inland seas. — De- 
scribe lochs, Voes, and fiords. 

Give some particulars about the depth of the ocean ; about its 
temperature ; about its saline contents. — Mention the usual 
degree of saltness of inland seas ; and what sea forms an excep- 
tion to the general rule. 

What is the freezing point of sea-water ? — Give some account 
of icebergs. 

Does it appear that sea-water has any color ? — Is its color 
sometimes influenced by its bed ? — Also by the presence of 
minute animals ? — What causes the luminous appearance of the 
ocean ? 

VIII. Tides, Waves, and Currents, (p. 68.) 

What causes the perpetual movement of the waters of the 
ocean ? — By what attraction are the waters retained in their 
bed on the earth's surface? — By what attraction is the great 
primary or tidal wave formed ? — How is ebb-tide or low water 
on our shores produced ? — How is flood-tide or high water pro- 
duced ? — What are spring tides ? — State the course of the At- 
lantic tidal wave ; and the difterence between high and low 
water at various places. 

Describe secondary or wind waves. — Describe the ground 
sea. 

What causes the currents of the ocean ? — And which are the 
most remarkable currents ? — Describe the polar currents. — 
Also the equatorial currents. — And the great system of cur- 
rents commencing in the Antarctic Seas. — Describe the Gulf 
Stream. 

IX. The Atmosphere, (p. 75.) 

Describe the earth's atmosphere ; and mention its height. — 
Of what is atmospheric air composed .' — Give some account of 



EXERCISES FOR EXAMINATION* 147 

the elasticity and the density of air. — Mention the consequences 
to which these gives rise. — Slate what is meant by the term 
"weight of an atmosphere;" and give some particulars about 
the barometer. 

What eflfects are produced on the temperature of the air by 
height above the sea-level ? 

What appears to give rise to winds ? — Give some particulars 
about winds. — Give an account of the trade- winds. — What 
causes south-westerly and north-westerly winds to prevail in 
higher latitudes ? — Give a description of monsoons. — What 
causes sea-breezes, and land-breezes ? 

What are hurricanes ? and what are typhoons and ox-eyes ? — 
How do tornadoes, pamperas, and arched squalls differ from hur- 
ricanes ? 

Describe the sirocco, solano, simun or simoon, and also the 
harmattan. 

In what state is water always present in the atmosphere ? and 
by what means does it find its way there ? — How is dew formed ? 
and when is it most abundantly deposited ? — On what substance 
is dew usually most copiously deposited ? 

When are mists and fogs likely to be formed ? 

How are clouds formed ? and of what do they consist ? — Men- 
tion also how rain is formed, and under what circumstances hail 
and snow are formed. 

What names are given to the principal forms of clouds ? — De- 
scribe the four principal kinds of clouds. — At what height in 
the atmosphere is the zone of clouds ? and which are the highest, 
and which the lowest clouds ? — Mention the names of the com- 
binations of the principal kinds of clouds. 

In what parts of the earth does the largest quantity of rain 
fall ? — Is it more abundant in the New than in the Old World ? 
Mention the rainless districts of the earth. — State the cause of 
the difference in the amount of rain in different regions. — What 
difference is there in the quantity of rain in the eastern and 
western parts of the British Isles ? 



148 EXERCISES FOR EXAMINATION. 

Give some particulars about rainy and dry seasons; and also 
relativeto the belt or zone called the " variables." — Give an 
account of the fall of rain in intertropical countries, and in 
countries beyond the tropics. 

X. Climate, (p. 95.) 

What is meant by the term climate ? — What are the most 
prominent causes of diversity of climate ? 

What is the grand agent in diffusing heat over the earth's 
surface? — Mention the effects produced by the earth's diurnal 
rotation ; and also the beneficial results from its inclined position 
in its orbit. 

How far does the artificial division of the earth into torrid, 
frigid, and temperate zones correspond with the climates of 
those regions ? 

Mention another leading cause of the diversity of climate ? — 
"What is signified when we speak of an insular climate ? — What 
by an excessive climate ? — Mention an instance of the effects 
produced by a large surface of water in tempering or moderating 
the climate of some regions of the earth. 

Mention another leading cause of the diversity of climate ; and 
give an account of the height of the snow-line in different re- 
gions. — Refer to the tabular view for its height in various lati- 
tudes. — What appears to be the cause of its greater height at 
certain distances from the equator, than under that line ? — 
Mention the beneficial results arising from the different tempera- 
ture at different heights. — Describe the eflects produced on 
vegetation by elevation above the sea-level, in the hot regions of 
the earth. 

Give some account of the temperature of mountains near 
table-lands. — Mention the Himalaya Mountains as an example; 
and state some particulars about isolated mountains in different 
climates. 

What effects are produced on climate by the nature of the soil ? 



EXERCISES FOR EXAMINATION. 149 

—What by the prevailing winds ? — How do mountain ranges 
affect climate ? — What efifects are produced by the currents of 
the ocean ? — Give some account of the Sea of Sargasso ; and 
mention the effects it produces on the temperature of the North- 
ern Ocean. 

What districts usually possess more excessive climates ? — 
Does the temperature vary as much in intertropical, as in tem- 
perate regions ? 

What are isothermal lines ? — Do they run parallel with the 
equator ? — What are isotheral and isochimenal lines ? — What 
is the average degree of heat of the line of highest temperature ; 
— What regions does it cross ? — Which is considered to form 
the hottest region of the earth ? 

XI. Electricity and Magnetism, (p. 109.) 

Does Electricity act any part in the natural world ? — Mention 
what is meant by ordinary electricity, and how it may be called 
forth, and what is meant by voltaic electricity. 

What is meant when it is said that any substance is positively 
electrified ? and what when negatively electrified ? — Give some 
particulars about the electrical state of substances, and of the 
effects produced if they come in contact. 

In what state of electricity is the earth considered always to 
be J and in what pure atmospheric air? — Mention, also, by 
what means the electrical equilibrium of the air is liable to be 
disturbed, and how it is sometimes restored. — At what periods 
of the day and of the year is electrical intensity greatest ? 

What effects does it appear that voltaic electricity is continu- 
ally producing in the earth's crust ? and what substances are 
supposed to be formed by its powerful agency ? 

"What is terrestrial magnetism ? — Under what heads may it 
be considered ? — How may the magnetic, or attractive power of 
the loadstone be imparted to iron or steel, or how may it become 
magnetized ? — What is meant by the magnetic direction of the 
compass needle ? — In what direction does the needle point ? — 



150 EXERCISES FOR EXAMINATION. 

Is this subject to variation, and what is the variation termed ? — 
What is meant by lines of eastward and westward variation ? — 
What by lines of no variation ? 

What is meant when we speak of the dip or inclination of the 
magnetic needle ? — Describe the magnetic equator. 

XII. Geographical Distribution op Plants, (p. 114.) 

Give some particulars about the plants on the earth's surface ? 
Mention the adaptation of plants to all parts of the earth. 

Into what classes are plants naturally divided ? 

Describe cryptogamic, or a-cotyledonous plants. — Describe 
endogenous, or mono-cotyledonous plants. — Describe exogenous, 
or di-cotyledonous plants. 

Which class of plants includes the greatest number of species ? 
— What is the proportion of the different classes in different 
zones ? 

Describe perennial annual, and biennial plants. — Describe 
deciduous plants ; and mention in what parts of the earth they 
most abound. — Give an account of the peculiar character of 
the evergreen trees of hot regions, and that of those of cold 
regions. 

From what do plants derive their nourishment? — What ef- 
fects are produced on plants by light ? — Give some particulars 
about the composition of plants, and what is required to bring 
them to perfection. 

In what regions of the earth are the vegetable productions 
most varied ? — State the relative proportion in the different 



Are the same plants met with in all regions possessing 
similar climates? — How is the earth divided into botanical 
regions ? 

Give some account of the correspondence between the plants of 
Arctic regions and those of high mountains in hot climates ; also 
of the resemblance between those of temperate regions and of 
the middle region of such mountains. — Give Baron Humboldt's 



EXERCISES FOR EXAMINATION. 151 

diTision of the earth into eight zones. — Give the scale of vege- 
tation at various heights in temperate Europe. 

On what account is it important to be acquainted with the 
zones and climates in which plants will succeed ? — Mention the 
highest northern limit of the successful cultivation of wheat, oats, 
and barley, in Europe. — State how gratifying the pursuit of 
this science is likely to prove. 

XIII. Geographical Distribution of Animals, (p. 126.) 

Does it appear that the distribution of animals on the earth's 
surface is influenced by climate ? 

Mention the four great departments of the animal kingdom. 

Why are vertebrated animals so named, and what is their pe- 
culiar characteristic ? and what animals are included in this 
division ? — Into what four classes are vertebrated animals sub- 
divided ? 

Why are articulated so named, and what animals are included 
in this division ? — State, also, what animals are called crusta- 
ceous. — Why are molluscous animals so named, and what ani- 
mals belong to this division ? — Why are radiated animals so 
named, and what animals belong to this division of the animal 
kingdom ? 

Which of these four divisions ranks as the lowest among living 
creatures ? and which is the highest ? — Which forms the highest 
class among vertebrated animals ? 

Give the meaning of the several terms species, genus, order, 
class, and department ; and give the example. 

Do we find that certain species of animals are peculiar to par- 
ticular regions ? — Mention some of the animals peculiar to the 
Old World. — Mention some animals peculiar to the New 
World. — What animals are met with in the more northerly re- 
gions of both continents ? — Mention the peculiarity of the group 
of animals inhabiting Australia. 

Give some account of the geographical distribution of birds. 



152 EXERCISES FOR EXAMINATION. 

Are the animals inhabiting warm regions usually more con- 
spicuous than those of temperate regions ? 

Give some account of the adaptation of animals to the regions 
which form their natural habitations ; and give instances of the 
changes which sometimes take place when animals are removed 
to other climates. 

XIV. Geographical Distribution of Man. (p. 133.) 

How many languages or dialects are now spoken in the world ? 
— What are languages called, which appear to be derived from 
the same root or origin ? — Why is one family of languages called 
" Semitic ? '' — Give an account of the Indo-European family of 
languages. 

What are schools of languages, or classes of languages ? — 
What languages are included in the mono-syllabic class ? — 
What languages are included under the class called poly-syn- 
thetic ? 

To what consequences did the dispersion of mankind appa- 
rently lead ? — Mention the leading divisions or varieties of the 
human race. 

What are the characteristics of the Caucasian race ? — What 
regions have they occupied, and at present still occupy ? — What 
are the characteristics of the Mongolian race, and what regions 
do they occupy ? — What are the characteristics of the Ethiopian 
or Negro race, and what regions do they occupy ? — What are 
the characteristics of the Malay or Malayan race, and what re- 
gions do they occupy ? — What are the characteristics of the 
American race, and what portion of the globe do they occupy ? 

What has tended to disunite mankind, and what may tend to 
restore union among the human race ? 



153 



aUESTIONS FOR INVESTIGATION. 

TO THE TEACHEE. 

After closing the study of this book, it will 
be well to enter upon these questions, which are 
intended to call into action the reason of the pu- 
pil as well as his memory. In many instances 
it will be necessary to direct the pupil to other 
sources of information than those mentioned in 
the preface, and to give oral instruction to the 
class. 



What does Physical mean ? 
What is meant by commerce ? 
Can a knowledge of Physical Geography pro- 
mote Commerce ? How? 

What does the word diameter mean ? 
Has the earth more than one diameter ? 
Has it several of the same length ? 
What does spheroid mean ? spheroidal ? 



154 QUESTIONS FOR INVESTIGATION. 

How is the earth supposed to have obtained 
its spheroidal shape ? 

Suppose that a round ball of putty were placed 
on a rapidly revolving spindle, would it retain its 
round shape ? 

What shape would it assume ? 

What is meant by centrifugal force ? by cen- 
tripetal force ? 

Wille the centrifugal force be greater at the 
equator or at the poles ? Why ? 

Would a leaden bullet weigh the same at the 
equator as at the poles ? 

Would a pendulum vibrate with equal rapid- 
ity at the equator and at the poles ? 

Give the reason for your answer. 

How far is it from the poles to the centre of 
the earth ? 

What is the most common mineral found in 
the earth ? 

Is it commonly found pure ? 

What town do you think to be at the middle 
of Europe ? of America ? 

What is the middle of the Eastern Hemi- 
sphere ? of the Western ? 

You may name some benefits which result 
from the preponderance of water over land on 
the globe. 



QUESTIONS FOR INVESTIGATION. 155 

What is the chief cause of the unevenness of 
the land? 

If the earth presented a flat surface, what 
would be the consequence ? 

Which is the largest of the oceans ? 

Does the same climate always exist within the 
same zones ? 

K North America be considered as main land, 
what immense peninsula extends from it ? 

Name another immense peninsula. 

What country seems to have the most coast- 
line in proportion to its size ? What the least ? 

What country then has the most numerous 
harbors ? 

Compare Asia with South America in this 
respect ? 

Which way do most large peninsulas turn ? 

Mention exceptions ? 

Mention some of the uses of mountains ? 

What kind of vegetation would you expect to 
find at the summits of the highest mountains ? 

Describe a glacier. 

How fast are they supposed to move ? 

What are avalanches ? 

Can you find an account of an avalanche 
among the White Mountains ? 

From what do volcanoes receive their name ? 

From what is the crater called ? 



156 QUESTIONS FOR INVESTIGATION. 

What does steppe mean ? 

Where are steppes found ? 

What important use do deserts subserve ? 

How are the lowland plains of North America 
situated ? 

Point out a water-shed in Europe ; in Asia ; 
in Africa? 

What is a rolling prairie ? 

What general shape have islands which lie 
along the coasts of continents ? Give examples. 

How can you account for this ? 

Generally speaking, are the largest islands 
found near to, or remote from, the shore ? 

What exceptions can you name ? 

What are volcanic islands ? 

Give examples of them ? 

Are volcanic islands always permanent ? 

Can you find any instance of the disappear- 
ance of volcanic islands ? 

How are coral rocks formed ? 

What are Atolls ? 

What are the principal causes of change in the 
earth's surface ? 

What are the advantages of such changes to 
a country ? 

How are waterfalls formed ? 

Can you show the wasting effect of the water 
at the Falls of Niagara ? 



QUESTIONS FOR INVESTIGATION. 157 

How fast are these Falls thought to recede ? 

Then how long has it taken for them to recede 
from Queenstown to their present place, a dis- 
tance of seven miles ? 

How are lakes formed ? 

What is the cause of whklpools ? 

Give an instance of one. 

What peculiar danger do they bring to mari- 
ners ? 

What are inland seas ? 

How do they differ from lakes ? 

Describe the fiords of Norway. 

How is the surface of the earth heated ? 

Is the earth nearer the sun in summer or in 
winter ? 

Upon what does the amount of heat depend ? 

What do you mean by perpendicular rays ? 
by slant rays ? 

Do perpendicular or slant rays give the more 
heat? 

Over what zone does the sun's course through 
the year lie ? 

Why are the tropics so called ? 

Does the sun move round the earth, or the 
earth round the sun ? 

If the axis of the earth were not inclined, 
where would the sun's rays fall perpendicularly ? 



158 * QUESTIONS FOR INVESTIGATION. 

How often in the year does the sun shirie 
vertically on the equator ? 

Why are these occasions called equinoxes ? 

"When does the sun shine vertically on the 
Tropic of Cancer ? of Capricorn ? 

What are these occasions termed ? 

When the sun shines vertically on the Tropic 
of Cancer, how many degrees beyond the North 
Pole can any of the slant rays fall ? 

How many beyond the South Pole, when he 
is at the Tropic of Capricorn ? 

Then what do the Arctic and Antarctic circles 
show? 

How long is the day at the North Pole ? 
Why? 

The night ? Why ? 

How many days and nights in the year at the 
South Pole? Why? 

If the sun were shining vertically now on the 
Tropic of Cancer, which would be the longer 
here, the day or night ? 

If upon the Tropic of Capricorn ? 

If upon the Equator ? 

What is the shortest day of the year to per- 
sons in the Northern Hemisphere ? the longest ? 

(The questions given immediately above must 
be resolved with the assistance of a globe.) 



QUESTIONS FOR INVESTIGATION. 159 

When it is noon at London, what will be the 
time at Boston ? 

At six o'clock, A. M. at Boston, what will be 
the time at St. Louis ? at St. Petersburg ? 

When it is three o'clock, P. M. at London, 
what will be the time at Bordeaux ? 

What is the latitude of Cape Horn ? 

What is the Aurora Borealis ? 

How is it thought to be produced? 

Is a garden bean a cryptogamous or a phaeno- 
gamous plant ? 

Is it mono-cotyledonous or di-cotyledonous ? 

Is it endogenous or exogenous ? 

What is the effect of light on the colors of 
blossoms ? 

Describe the banian tree, and quote Milton's 
description of it (P. L. ix, 1100). 

Give so far as you can the flora of the state in 
which you live. 

Give its fauna. 



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